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WM8751L
STEREO DAC FOR PORTABLE AUDIO APPLICATIONS
DESCRIPTION
The WM8751L is a low power, high quality stereo DAC with integrated headphone and loudspeaker amplifiers, designed to reduce external component requirements in portable digital audio applications. The on-chip headphone amplifiers can deliver 40mW into a 16 load. Advanced on-chip digital signal processing performs bass and treble tone control. The WM8751L can operate as a master or a slave, with various master clock frequencies including 12 or 24MHz for USB devices or standard 256fs rates like 12.288MHz and 24.576MHz. Different audio sample rates such as 96kHz, 48kHz, 44.1kHz are generated directly from the master clock without the need for an external PLL. The WM8751L operates on supply voltages from 1.8V up to 3.6V, although the digital core can operate on a separate supply down to 1.42V, saving power. Different sections of the chip can also be powered down under software control. The WM8751L is supplied in a very small and thin 5x5mm QFN package, ideal for use in hand-held and portable systems.
FEATURES
* * * * * * * * DAC SNR 98dB, THD -95dB (`A' weighted @ 48kHz, 3.3V) On-chip 400mW BTL Speaker Driver (mono) On-chip Headphone Driver 40mW output power on 16 / 3.3V THD -80dB at 20mW, SNR 90dB with 16 load Stereo and Mono Line-in mix into DAC output Separately Mixed Stereo and Mono Outputs Digital Tone Control and Bass Boost Low Power Low Supply Voltages Analogue 1.8V to 3.6V Digital core: 1.42V to 3.6V Digital I/O: 1.42V to 3.6V 256fs / 384fs or USB master clock rates: 12MHz, 24MHz Audio sample rates: 8, 11.025, 12, 16, 22.05, 24, 32, 44.1, 48, 88.2, 96kHz generated internally from master clock 32-pin QFN package, 5x5x0.9mm size, 0.5mm lead pitch
* * *
APPLICATIONS
* * * Digital Audio Player MP3 Phone Minidisc Player
BLOCK DIAGRAM
MONOIN+ MONOINLINEINL LINEINR
DBVDD
DCVDD
DGND
HPGND
HPVDD
W
WM8751L
LEFT LD2LO MIXER
DIFF. IN
LI2LO
MONOOUT ROUT1 VREF
M U X
-1
OUT3
LOUT1 CSB SDIN SCLK MODE
RD2LO
CONTROL INTERFACE
DAC DIGITAL FILTERS
VREF LD2MO MONO MIXER
MI2LO LI2MO
LOUT1VOL
MONOOUT
RD2MO RI2MO MI2RO MONOVOL
BCLK DACLRC DACDAT
DIGITAL AUDIO INTERFACE
TONE CONTROL DAC
RIGHT LD2RO MIXER
ROUT1
RD2RO RI2RO ROUT1VOL
MCLK
VREF -1 50K 50K LOUT2VOL ROUT2 INV
LOUT2 Loudspeaker L - (-R) = L+R ROUT2
ROUT2VOL
AVDD
AGND
VREF
VMID
HPDETECT
WOLFSON MICROELECTRONICS PLC www.wolfsonmicro.com
Product Preview, May 2003, Rev 1.42 Copyright 2003 Wolfson Microelectronics Ltd.
WM8751L PIN CONFIGURATION
HPDETECT
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ORDERING INFORMATION
ORDER CODE
HPVDD AGND AVDD
TEMPERATURE RANGE -25C to +85C
PACKAGE 32-pin QFN (5x5x0.9mm)
24
23
22
21
20
VREF
VMID
WM8751LEFL
NC
NC
19
18
17
MONOIN- 25 MONOIN+ 26 LINEINR LINEINL
27 28
16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8
LOUT2 ROUT2 HPGND LOUT1 ROUT1 OUT3 MONOOUT AGND2
MODE 29 CSB 30 SDIN
31
SCLK 32
DBVDD
DACDAT
DGND
DCVDD
MCLK
BCLK
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DACLRC
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WM8751L
PIN DESCRIPTION
PIN # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 NAME MCLK DCVDD DBVDD DGND BCLK DACDAT DACLRC NC AGND2 MONOOUT OUT3 ROUT1 LOUT1 HPGND ROUT2 LOUT2 HPVDD AVDD AGND VREF VMID NC HPDETECT NC MONOINMONOIN+ LINEINR LINEINL MODE CSB SDIN SCLK TYPE Digital Input Supply Supply Supply Digital Input / Output Digital Input Digital Input / Output No Connect Supply Analogue Output Analogue Output Analogue Output Analogue Output Supply Analogue Output Analogue Output Supply Supply Supply Analogue Output Analogue Output No Connect Logic Input No Connect Analogue Input Analogue Input Analogue Input Analogue Input Digital Input Digital Input Digital Input/Output Digital Input Master Clock Digital Core Supply Digital Buffer (I/O) Supply Digital Ground (return path for both DCVDD and DBVDD) Audio Interface Bit Clock DAC Digital Audio Data Audio Interface Left / Right Clock No Internal Connection Internally connected to AGND. Leave this pin floating or connect to AGND. Mono Output Output 3 (can be used as Headphone Pseudo Ground) Right Output 1 (Line or Headphone) Left Output 1 (Line or Headphone) Supply for Analogue Output Drivers (LOUT1/2, ROUT1/2) Right Output 1 (Line or Headphone or Speaker) Left Output 1 (Line or Headphone or Speaker) Supply for Analogue Output Drivers (LOUT1/2, ROUT1/2, MONOUT) Analogue Supply Analogue Ground (return path for AVDD) Reference Voltage Decoupling Capacitor Midrail Voltage Decoupling Capacitor No Internal Connection Headphone / Speaker switch (referred to AVDD) No Internal Connection Negative end of MONOIN+, for differential mono signals Analogue Line-in to mixers (mono channel) Analogue Line-in to mixers (right channel) Analogue Line-in to mixers (left channel) Control Interface Selection Chip Select / Device Address Selection Control Interface Data Input / 2-wire Acknowledge output Control Interface Clock Input DESCRIPTION
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WM8751L ABSOLUTE MAXIMUM RATINGS
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Absolute Maximum Ratings are stress ratings only. Permanent damage to the device may be caused by continuously operating at or beyond these limits. Device functional operating limits and guaranteed performance specifications are given under Electrical Characteristics at the test conditions specified.
ESD Sensitive Device. This device is manufactured on a CMOS process. It is therefore generically susceptible to damage from excessive static voltages. Proper ESD precautions must be taken during handling and storage of this device.
CONDITION Supply voltages Voltage range digital inputs Voltage range analogue inputs Operating temperature range, TA Storage temperature prior to soldering Storage temperature after soldering Package body temperature (soldering 10 seconds) Package body temperature (soldering 2 minutes) Notes 1. 2. Analogue and digital grounds must always be within 0.3V of each other. All digital and analogue supplies are completely independent from each other.
MIN -0.3V DGND -0.3V AGND -0.3V -25C -65C
MAX +3.63V DBVDD +0.3V AVDD +0.3V +85C +150C +260C +183C
30C max / 85% RH max
RECOMMENDED OPERATING CONDITIONS
PARAMETER Digital supply range (Core) Digital supply range (Buffer) Analogue supplies range Ground SYMBOL DCVDD DBVDD AVDD, HPVDD DGND, AGND, HPGND TEST CONDITIONS MIN 1.42 1.8 1.8 TYP 2.0 2.0 2.0 0 MAX 3.6 3.6 3.6 UNIT V V V V
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WM8751L
ELECTRICAL CHARACTERISTICS
Test Conditions DCVDD = 1.5V, AVDD = HPVDD = 3.3V, TA = +25oC, 1kHz signal, fs = 48kHz, 24-bit audio data unless otherwise stated. PARAMETER Signal to Noise Ratio (A-weighted) Total Harmonic Distortion Channel Separation Full-scale Input Signal Level Signal to Noise Ratio Line-in to Line-Out (A-weighted) Total Harmonic Distortion Input Resistance (signal enters one mixer only) Input Resistance (signal enters two mixers) MONOIN- input resistance Programmable Gain Programmable Gain Step Size Mute Attenuation Analogue Outputs (LOUT1/2, ROUT1/2, MONOOUT) 0dB Full scale output voltage Programmable Gain Programmable Gain Steps Mute attenuation Channel Separation Headphone Output (LOUT1/2, ROUT1/2 with 16 or 32 Ohm load) Output Power per channel Total Harmonic Distortion PO THD Output power is very closely correlated with THD; see below. HPVDD=1.8V, RL=32 PO=5mW HPVDD=1.8V, RL=16 PO=5mW HPVDD=3.3V, RL=32, PO=20mW HPVDD=3.3V, RL=16, PO=20mW Signal to Noise Ratio (A-weighted) SNR HPVDD = 3.3V HPVDD = 1.8V 0.013 -78 0.013 -78 0.01 -80 0.01 -80 90 90 dB dB % 1kHz signal Monotonic 1kHz, full scale signal 80 -67 80 85 90 AVDD/3.3 +6 Vrms dB steps dB dB Monotonic RMONOINVINFS SNR SYMBOL SNR THD TEST CONDITIONS AVDD = 3.3V AVDD = 1.8V AVDD = 3.3V AVDD = 1.8V 1kHz signal AVDD = 3.3V AVDD = 1.8V AVDD = 3.3V AVDD = 1.8V THD RLINEIN AVDD = 3.3V AVDD = 1.8V PGA gain = 0dB PGA gain = +6dB PGA gain = 0dB PGA gain = +6dB any gain -15 3 TBD Analogue Mixer Inputs (LINEINL, LINEINR, MONOIN+) 1.0 0.516 95 90 -92 -92 20 10 10 5 20 +6 k dB dB dB dB dB k dB V rms MIN TYP 98 95 -95 -90 90 dB dB MAX UNIT dB DAC to Line-Out (LOUT1/2, ROUT1/2, MONOOUT with 10k / 50pF load)
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WM8751L
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Test Conditions DCVDD = 1.5V, AVDD = HPVDD = 3.3V, TA = +25oC, 1kHz signal, fs = 48kHz, 24-bit audio data unless otherwise stated. PARAMETER Output Power SYMBOL PO TEST CONDITIONS HPVDD=3.3V, RL=8 HPVDD=3.0V, RL=8 HPVDD=2.7V, RL=8 Signal to Noise Ratio (A-weighted) Total Harmonic Distortion SNR HPVDD=3.3V, RL=8 HPVDD=3.0V, RL=8 HPVDD=2.7V, RL=8 THD Po=150mW, RL=8, HPVDD=3.3V Po=300mW, RL=8 HPVDD=3.3V Analogue Reference Levels Midrail Reference Voltage Buffered Reference Voltage VREF source current VREF sink current Digital Input / Output Input HIGH Level Input LOW Level Output HIGH Level Output LOW Level VIH VIL VOH VOL 0.9xDBVDD 0.1xDBVDD 0.7xDBVDD 0.3xDBVDD V V V V VMID VREF IVREF IVREF -3% -3% AVDD/2 AVDD/2 +3% +3% 5 5 V V mA mA MIN TYP 400 300 230 75 75 75 -60 0.1 -50 0.3 dB % dB MAX UNIT mW Speaker Output (LOUT2/ROUT2 with 8 bridge tied load, ROUT2INV=1)
TERMINOLOGY
1. 2. Signal-to-noise ratio (dB) - SNR is a measure of the difference in level between the full scale output and the output with no signal applied. (No Auto-zero or Automute function is employed in achieving these results). Dynamic range (dB) - DR is a measure of the difference between the highest and lowest portions of a signal. Normally a THD+N measurement at 60dB below full scale. The measured signal is then corrected by adding the 60dB to it. (e.g. THD+N @ -60dB= -32dB, DR= 92dB). THD+N (dB) - THD+N is a ratio, of the rms values, of (Noise + Distortion)/Signal. Channel Separation (dB) - Also known as Cross-Talk. This is a measure of the amount one channel is isolated from the other. Normally measured by sending a full scale signal down one channel and measuring the other.
3. 4.
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WM8751L
OUTPUT PGA'S LINEARITY
10.000 0.000 Output PGA Gains -10.000 Measured Gain [dB] -20.000 -30.000 -40.000 -50.000 -60.000 -70.000 40 50 60 70 80 90 100 110 120 130 XXXVOL Register Setting (binary) LOUT1 ROUT1 LOUT2 ROUT2 MONOOUT
2.000 1.750 Output PGA Gain Step Size 1.500 1.250 1.000 0.750 LOUT1 0.500 0.250 0.000 40 50 60 70 80 90 100 110 120 130 ROUT1 LOUT2 ROUT2 MONOOUT
Step Size [dB]
XXXVOL Register Setting (binary)
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WM8751L
HEADPHONE OUTPUT THD VERSUS POWER (SIMULATION)
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0 Headphone Pow er vs THD+N (32Ohm load) -20
THD+N (dB)
-40
AVDD=1.8V AVDD=1.8V, capless AVDD=3.3V
-60
AVDD=3.3V, capless
-80
-100 0 5 10 15 Pow er (m W) 20 25 30
0 Headphone Pow er vs THD+N (16Ohm load) -20
THD+N (dB)
-40
AVDD=1.8V AVDD=1.8V, capless AVDD=3.3V
-60
AVDD=3.3V, capless
-80
-100 0 10 20 30 Pow er (m W) 40 50 60
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WM8751L
SPEAKER OUTPUT THD VERSUS POWER (SIMULATION)
-10 -20 -30 AVDD=1.8V -40 -50 -60 -70 0 100 200 300 400 500 Pow er (m W) Speaker Pow er vs THD+N (8Ohm BTL load) AVDD=2.5V AVDD=3.3V
THD+N (dB)
10 Speaker Power vs THD+N (8 Ohm BTL load) 8
THD+N (%)
6
AVDD=1.8V AVDD=2.5V AVDD=3.3V
4
2
0 0 100 200 300 400 500 Power (mW)
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WM8751L POWER CONSUMPTION
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The power consumption of the WM8751L depends on the following factors. * Supply voltages: Reducing the supply voltages also reduces supply currents, and therefore results in significant power savings. * Operating mode: Power consumption is lower in mono modes than in stereo, as one DAC is switched OFF. Unused analogue outputs should be switched off.
Control Register Bit OFF
R25 VMIDSEL
R26 (1Ah)
R24 R23 R38 DACOSR DMEN VSEL
Other settings
AVDD
DCVDD
DBVDD
HPVDD
Tot. Power
VREF DACL DACR LOUT1 ROUT1 LOUT2 ROUT2 MONO OUT3
00 0 0 0 0 0 0 0 0 0
0
Low-power standby (LPS) using 500 KOhm VMID string Playback to Line-out
10 1 0 0 0 0 0 0 0 0
0
01 1 1 1 0 0 1 1 0 0
0
Playback to Line-out (64x oversampling mode) Playback to 16 Ohm headphone using caps on HPOUTL/R Playback to 16 Ohm headphone capless mode using OUT3 Playback to 8 Ohm BTL speaker Headphone Amp line-in to 16 Ohm h/phone Speaker Amp line-in to 8 Ohm speaker Phone Call diff. mono line-in to h/phone, diff. mono line-out to TX
01 1 1 1 1 1 0 0 0 0
1
01 1 1 1 1 1 0 0 0 0
0
01 1 1 1 1 1 0 0 0 1
0
01 1 1 1 0 0 1 1 0 0
0
01 1 0 0 1 1 0 0 0 0
0
01 1 0 0 0 0 1 1 0 0
0
01 1 0 0 1 1 0 0 1 1
0
11 01 00 11 01 00 11 01 00 11 01 00 11 01 00 11 01 00 11 01 00 11 01 00 11 01 00 11 01 00
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1
Clocks stopped
R24, OUT3SW=00
R24, ROUT2INV=1
R24, ROUT2INV=1
V 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8
I (mA) TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD
V 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5
I (mA) TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD
V 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5 3.3 2.5 1.5
I (mA) TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD
V 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8 3.3 2.5 1.8
I (mA) TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD
(mW) <0.01 <0.01 <0.01 <0.02 <0.02 <0.02 40 20 9 34 19 8.5 40 20 9 TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD TBD
Table 1 Supply Current Consumption (Target)
Notes: 1. 2. 3. TA = +25oC, Slave Mode, fs = 48kHz, MCLK = 12.288 MHz (256fs), 24-bit data All figures are quiescent, with no signal. The power dissipated in the headphone itself is not included in the above table.
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WM8751L
SIGNAL TIMING REQUIREMENTS
SYSTEM CLOCK TIMING
tMCLKL MCLK tMCLKH tMCLKY
Figure 1 System Clock Timing Requirements Test Conditions DBVDD = 3.3V, DGND = 0V, TA = +25oC, Slave Mode fs = 48kHz, MCLK = 256fs, 24-bit data, unless otherwise stated. PARAMETER System Clock Timing Information
MCLK System clock pulse width high MCLK System clock pulse width low MCLK System clock cycle time
SYMBOL tMCLKL tMCLKH tMCLKY
MIN 16 16 27
TYP
MAX
UNIT ns ns ns
AUDIO INTERFACE TIMING - MASTER MODE
BCLK (Output) tDL DACLRC (Output) tDST DACDAT tDHT
Figure 2 Digital Audio Data Timing - Master Mode (see Control Interface) Test Conditions DBVDD = 3.3V, DGND = 0V, TA = +25oC, Slave Mode fs = 48kHz, MCLK = 256fs, 24-bit data, unless otherwise stated. PARAMETER System Clock Timing Information
DACLRC propagation delay from BCLK falling edge DACDAT setup time to BCLK rising edge DACDAT hold time from BCLK rising edge
SYMBOL tDL tDST tDHT
MIN
TYP
MAX 10
UNIT ns ns ns
10 10
AUDIO INTERFACE TIMING - SLAVE MODE
tBCH BCLK tBCY tBCL
DACLRC tDS DACDAT tLRH tLRSU
Figure 3 Digital Audio Data Timing - Slave Mode (see Control Interface)
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WM8751L
Test Conditions
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DBVDD = 3.3V, DGND = 0V, TA = +25oC, Slave Mode fs = 48kHz, MCLK = 256fs, 24-bit data, unless otherwise stated. PARAMETER System Clock Timing Information
BCLK cycle time BCLK pulse width high BCLK pulse width low DACLRC setup time to BCLK rising edge DACLRC hold time from BCLK rising edge DACDAT hold time from BCLK rising edge
SYMBOL tBCY tBCH tBCL tLRSU tLRH tDH
MIN 50 20 20 10 10 10
TYP
MAX
UNIT ns ns ns ns ns ns
CONTROL INTERFACE TIMING - 3-WIRE MODE
tCSL CSB tCSS tSCL tSCS tCSH
tSCY tSCH SCLK
SDIN tDSU tDHO
LSB
Figure 4 Control Interface Timing - 3-Wire Serial Control Mode Test Conditions DBVDD = 3.3V, DGND = 0V, TA = +25oC, Slave Mode, fs = 48kHz, MCLK = 256fs, 24-bit data, unless otherwise stated. PARAMETER Program Register Input Information SCLK rising edge to CSB rising edge SCLK pulse cycle time SCLK pulse width low SCLK pulse width high SDIN to SCLK set-up time SCLK to SDIN hold time CSB pulse width low CSB pulse width high CSB rising to SCLK rising Pulse width of spikes that will be suppressed tSCS tSCY tSCL tSCH tDSU tDHO tCSL tCSH tCSS tps 500 200 80 80 40 40 40 40 40 0 5 ns ns ns ns ns ns ns ns ns ns SYMBOL MIN TYP MAX UNIT
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WM8751L
CONTROL INTERFACE TIMING - 2-WIRE MODE
t3 t5 t4 t6 t2 t8 t3
SDIN
SCLK t1 t9 t7
Figure 5 Control Interface Timing - 2-Wire Serial Control Mode Test Conditions DBVDD = 3.3V, DGND = 0V, TA = +25oC, Slave Mode, fs = 48kHz, MCLK = 256fs, 24-bit data, unless otherwise stated. PARAMETER Program Register Input Information SCLK Frequency SCLK Low Pulse-Width SCLK High Pulse-Width Hold Time (Start Condition) Setup Time (Start Condition) Data Setup Time SDIN, SCLK Rise Time SDIN, SCLK Fall Time Setup Time (Stop Condition) Data Hold Time Pulse width of spikes that will be suppressed t1 t2 t3 t4 t5 t6 t7 t8 t9 tps 0 600 900 5 0 600 1.3 600 600 100 300 300 400 kHz ns us ns ns ns ns ns ns ns ns SYMBOL MIN TYP MAX UNIT
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WM8751L DEVICE DESCRIPTION
INTRODUCTION
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The WM8751L is a low power audio DAC offering a combination of high quality audio, advanced features, low power and small size. These characteristics make it ideal for portable digital audio applications such as portable music players and smartphones. The device has a configurable digital audio interface where digital audio data is fed to the internal digital filters and then the DAC. The interface supports a number of audio data formats including I2S, DSP Mode (a burst mode in which frame sync plus 2 data packed words are transmitted), Left Justified and Right Justified formats, and can operate in master or slave modes. The on-chip digital filters perform tone control and digital volume control according to the user setting, and convert the audio data into oversampled bitstreams, which are passed to the left and right channel DACs. A multi-bit, low-order DAC architecture with dynamic element matching is used, delivering optimum performance with low power consumption. The DAC output signal enters an analogue mixer where analogue input signals can be added to it. The WM8751L has a total of six analogue output pins, which can be configured as stereo line-outs, mono line-outs, differential mono line-outs, stereo headphone outputs or differential mono (BTL) speaker outputs. The WM8751L master clock can be either an industry standard 256/384 fs clock or a 12MHz/24MHz USB clock. Sample rates of 8kHz, 11.025kHz, 12kHz, 16kHz, 22.05kHz, 32kHz, 44.1kHz, 48kHz, 88.2kHz and 96kHz can be generated directly from the master clock, without an external PLL. The digital filters are optimised for each sample rate. To allow full software control over all its features, the WM8751L offers a choice of 2 or 3 wire MPU control interface. It is fully compatible and an ideal partner for a wide range of industry standard microprocessors, controllers and DSPs. The design of the WM8751L has given much attention to power consumption without compromising performance. It operates at very low voltages, and includes the ability to power off parts of the circuitry under software control, including standby and power off modes.
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WM8751L
SIGNAL PATH
The WM8751L signal paths consists of digital filters, DACs, analogue mixers and output drivers. Each circuit block can be enabled or disabled separately using the control bits in register 26 (see "Power Management"). Thus it is possible to utilise the analogue mixing and amplification provided by the WM8751L, irrespective of whether the DACs are running or not. The WM8751L receives digital input data on the DACDAT pin. The digital filter block processes the data to provide the following functions:
* * * *
Digital volume control Tone control and Bass Boost Digital Mono Mix Sigma-Delta Modulation
Two high performance, sigma-delta audio DACs convert the digital data into two analogue signals (left and right). These can then be mixed with analogue signals from the LINEINL, LINEINR and MONOIN pins, and the mix is fed to the output drivers, LOUT1/ROUT1, LOUT2/ROUT2, and MONOOUT.
* * * *
LOUT1/ROUT1: can drive 16 or 32 stereo headphones or stereo line output. LOUT2/ROUT2: can drive an 8 mono speaker, stereo headphones or a stereo line-out. MONOOUT: line output designed to drive a 10k load. OUT3: multi-function output, may be used for capacitor-less headphone drive, differential mono-out, line-out or 32 earpiece driver.
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WM8751L
DIGITAL VOLUME CONTROL
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The WM8751L has on-chip digital attenuation from -127dB to 0dB in 0.5dB steps, allowing the user to adjust the volume of each channel separately. The level of attenuation for an eight-bit code X is given by: -0.5 x (255 - X) dB for 1 X 255; MUTE for X = 0
The LDVU and RDVU control bits control the loading of digital volume control data. When LDVU or RDVU are set to 0, the LDACVOL or RDACVOL control data is loaded into an intermediate register, but the actual gain does not change. Both left and right gain settings are updated simultaneously when either LDVU or RDVU are set to 1.
REGISTER ADDRESS R10 (0Ah) Left Channel Digital Volume
BIT 7:0
LABEL LDACVOL[7:0]
DEFAULT 11111111 ( 0dB )
DESCRIPTION Left DAC Digital Volume Control 0000 0000 = Digital Mute 0000 0001 = -127dB 0000 0010 = -126.5dB ... 0.5dB steps up to 1111 1111 = 0dB Left DAC Volume Update 0 = Store LDACVOL in intermediate latch (no gain change) 1 = Update left and right channel gains (left = LDACVOL, right = intermediate latch) Right DAC Digital Volume Control similar to LDACVOL Right DAC Volume Update 0 = Store RDACVOL in intermediate latch (no gain change) 1 = Update left and right channel gains (left = intermediate latch, right = RDACVOL)
8
LDVU
0
R11 (0Bh) Right Channel Digital Volume
7:0 8
RDACVOL[7:0] RDVU
11111111 ( 0dB ) 0
Table 2 Digital Volume Control
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WM8751L
TONE CONTROL
The WM8751L provides separate controls for bass and treble with programmable gains and filter characteristics. This function operates on digital audio data before it is passed to the audio DACs. Bass control can take two different forms:
*
Linear bass control: bass signals are amplified or attenuated by a user programmable gain. This is independent of signal volume, and very high bass gains on loud signals may lead to signal clipping. Adaptive bass boost: The bass volume is amplified by a variable gain. When the bass volume is low, it is boosted more than when the bass volume is high. This method is recommended because it prevents clipping, and usually sounds more pleasant to the human ear.
*
Treble control applies a user programmable gain, without any adaptive boost function. REGISTER ADDRESS R12 (0Ch) Bass Control BIT 7 LABEL BB 0 DEFAULT DESCRIPTION Bass Mode 0 = Linear bass control 1 = Adaptive bass boost Bass Filter Characteristic 0 = Low Cutoff (130 Hz at 48kHz sampling) 1 = High Cutoff (200 Hz at 48kHz sampling) Bass Intensity Code 0000 0001 0010 ... 0111 ... 1011-1101 1110 1111 R13 (0Dh) Treble Control 6 TC 0 BB=0 +9dB +9dB +7.5dB (1.5dB steps) 0dB (1.5dB steps) -6dB -6dB BB=1 15 (max) 14 13 ... 8 ... 4-2 1 (min) Bypass (OFF)
6
BC
0
3:0
BASS
1111 (OFF)
Treble Filter Characteristic 0 = High Cutoff (8kHz at 48kHz sampling) 1 = Low Cutoff (4kHz at 48kHz sampling) Treble Intensity 0000 or 0001 = +9dB 0010 = +7.5dB ... (1.5dB steps) 1011 to 1110 = -6dB 1111 = Disable
3:0
TRBL
1111 (Disabled)
Table 3 Tone Control Note: 1. All cut-off frequencies change proportionally with the DAC sample rate.
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WM8751L
DIGITAL TO ANALOGUE CONVERTER (DAC)
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Treble and linear bass enhancement may produce signals that exceed full-scale. In order to avoid limiting under these conditions, it is recommended to set the DAT bit to attenuate the digital input signal by 6dB. The gain at the outputs should be increased by 6dB to compensate for the attenuation. Cut-only tone adjustment and adaptive bass boost cannot produce signals above fullscale and therefore do not require the DAT bit to be set. After passing through the tone control filters, digital `de-emphasis' can be applied to the audio data if necessary (e.g. when the data comes from a CD with pre-emphasis used in the recording). Deemphasis filtering is available for sample rates of 48kHz, 44.1kHz and 32kHz. The WM8751L also has a Soft Mute function, which gradually attenuates the volume of the digital signal to zero. This function is enabled by default. To play back an audio signal, the WM8751L must first be unmuted by setting the DACMU bit to zero. REGISTER ADDRESS R5 (05h) DAC Control BIT 7 LABEL DAT DEFAULT 0 DESCRIPTION DAC 6dB attenuate enable 0 = disabled (0dB) 1 = -6dB enabled DAC Digital Soft Mute 1 = mute 0 = no mute (signal active) De-emphasis Control 11 = 48kHz sample rate 10 = 44.1kHz sample rate 01 = 32kHz sample rate 00 = No De-emphasis
3
DACMU
1
2:1
DEEMPH
00
Table 4 DAC Control The digital audio data is converted to oversampled bit streams in the on-chip, true 24-bit digital interpolation filters. The bitstream data enters two multi-bit, sigma-delta DACs, which convert them to high quality analogue audio signals. The multi-bit DAC architecture reduces high frequency noise and sensitivity to clock jitter. It also uses a Dynamic Element Matching technique for high linearity and low distortion. In normal operation, the left and right channel digital audio data are converted to analogue in two separate DACs. However, it is also possible to disable one channel, so that the same signal (left or right) appears on both analogue output channels. Additionally, there is a mono-mix mode where the two audio channels are mixed together digitally and then converted to analogue using only one DAC, while the other DAC is switched off. The mono-mix signal can be selected to appear on both analogue output channels (see Analogue Outputs). REGISTER ADDRESS R23 (17h) Additional (1) BIT 5:4 LABEL DMONOMIX[1:0] DEFAULT 00 DESCRIPTION DAC mono mix 00: stereo 01: mono ((L+R)/2) into DACL, `0' into DACR 10: mono ((L+R)/2) into DACR, `0' into DACL 11: mono ((L+R)/2) into DACL & DACR
Table 5 DAC Mono Mix Select
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WM8751L
LINE INPUTS AND OUTPUT MIXERS
The WM8751L provides the option to mix the DAC output signal with analogue line-in signals from the LINEINL, LINEINR and MONOIN pins. The level of the mixed-in signals can be controlled with PGAs (Programmable Gain Amplifiers). LINEINL, LINEINR, MONOIN+ and MONOIN- are high impedance, low capacitance AC coupled analogue inputs. They are biased internally to the reference voltage VREF. Whenever these inputs are muted or the device placed into standby mode, the inputs remain biased to VREF using special anti-thump circuitry. This reduces any audible clicks that may otherwise be heard when re-activating the inputs.
REGISTER ADDRESS R34 (22h) Left Mixer (1)
BIT 8
LABEL LD2LO 0
DEFAULT
DESCRIPTION Left DAC to Left Mixer 0 = Disable (Mute) 1 = Enable Path LINEINL Signal to Left Mixer 0 = Disable (Mute) 1 = Enable Path LINEINL Signal to Left Mixer Volume 000 = +6dB ... (3dB steps) 111 = -15dB Right DAC to Left Mixer 0 = Disable (Mute) 1 = Enable Path MONOIN Signal to Left Mixer 0 = Disable (Mute) 1 = Enable Path MONOIN Signal to Left Mixer Volume 000 = +6dB ... (3dB steps) 111 = -15dB
7
LI2LO
0
6:4
LI2LOVOL
101 (-9dB)
R35 (23h) Left Mixer (2)
8
RD2LO
0
7
MI2LO
0
6:4
MI2LOVOL
101 (-9dB)
Table 6 Left Output Mixer Control
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WM8751L
REGISTER ADDRESS R36 (24h) Right Mixer (1) BIT 8 LABEL LD2RO 0 DEFAULT
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DESCRIPTION Left DAC to Right Mixer 0 = Disable (Mute) 1 = Enable Path MONOIN Signal to Right Mixer 0 = Disable (Mute) 1 = Enable Path MONOIN Signal to Right Mixer Volume 000 = +6dB ... (3dB steps) 111 = -15dB Right DAC to Right Mixer 0 = Disable (Mute) 1 = Enable Path LINEINR Signal to Right Mixer 0 = Disable (Mute) 1 = Enable Path LINEINR Signal to Right Mixer Volume 000 = +6dB ... (3dB steps) 111 = -15dB
7
MI2RO
0
6:4
MI2ROVOL
101 (-9dB)
R37 (25h) Right Mixer (2)
8
RD2RO
0
7
RI2RO
0
6:4
RI2ROVOL
101 (-9dB)
Table 7 Right Output Mixer Control
REGISTER ADDRESS R38 (26h) Mono Mixer (1)
BIT 8
LABEL LD2MO 0
DEFAULT
DESCRIPTION Left DAC to Mono Mixer 0 = Disable (Mute) 1 = Enable Path LINEINL Signal to Mono Mixer 0 = Disable (Mute) 1 = Enable Path LINEINL Signal to Right Mono Volume 000 = 0dB ... (3dB steps) 111 = -21dB Right DAC to Mono Mixer 0 = Disable (Mute) 1 = Enable Path LINEINR Signal to Mono Mixer 0 = Disable (Mute) 1 = Enable Path LINEINR Signal to Mono Mixer Volume 000 = 0dB ... (3dB steps) 111 = -21dB
7
LI2MO
0
6:4
LI2MOVOL
101 (-9dB)
R39 (27h) Mono Mixer (2)
8
RD2MO
0
7
RI2MO
0
6:4
RI2MOVOL
101 (-9dB)
Table 8 Mono Output Mixer Control Note: The mono mixer has half the gain of the left and right mixers (i.e. 6dB less), to ensure that the left and right channels can be mixed to mono without clipping.
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WM8751L
DIFFERENTIAL MONO LINE-IN
The WM8751L can take either a single-ended or a differential mono signal and mix it into the LOUT1/2 and ROUT1/2 outputs. In both cases, LINEINL and LINEINR still remain available as stereo line-in. Differential mono input mode is enabled by setting the DMEN bit, as shown below. REGISTER ADDRESS R38 (26h) Mono Mixer (1) BIT 0 LABEL DMEN 0 DEFAULT DESCRIPTION Differential mono line-in enable 0 = Single-ended line-in from MONOIN+ 1 = Differential line-in
Table 9 Differential Mono Line-in Enable
DEVICE WITH DIFFERENTIAL MONO OUTPUT
MONO OUT(-) MONO OUT(+)
MONOIN+
MONOIN-
DMEN = 1 (ON)
LEFT LD2LO MIXER
DIFF. IN
LI2LO
LINEINL LINEINR
LOUT1
RD2LO
DAC
LD2MO VREF MONO MIXER
MI2LO LI2MO
LOUT1VOL
MONOOUT
RD2MO RI2MO MI2RO MONOVOL
DAC
RIGHT LD2RO MIXER
ROUT1
RD2RO RI2RO ROUT1VOL
LOUT2
LOUT2VOL ROUT2 INV
W
WM8751L
-1
Loudspeaker L - (-R) = L+R ROUT2
ROUT2VOL
Figure 6 Differential Mono Line-in Configuration
DEVICE WITH SINGLE-ENDED MONO OUTPUT
MONO OUT
MONOIN- (connect to VREF)
MONOIN+
DMEN = 0 (OFF)
LEFT LD2LO MIXER
DIFF. IN
LI2LO
LINEINL LINEINR
LOUT1
RD2LO
DAC
LD2MO VREF MONO MIXER
MI2LO LI2MO
LOUT1VOL
MONOOUT
RD2MO RI2MO MI2RO MONOVOL
DAC
RIGHT LD2RO MIXER
ROUT1
RD2RO RI2RO ROUT1VOL
LOUT2
LOUT2VOL ROUT2 INV
W
WM8751L
-1
Loudspeaker L - (-R) = L+R ROUT2
ROUT2VOL
Figure 7 Single-ended Mono Line-in Configuration
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WM8751L
ANALOGUE OUTPUTS
ENABLING THE OUTPUTS
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Each analogue output of the WM8751L can be separately enabled or disabled. The analogue mixer associated with each output is powered on or off along with the output pin. All outputs are disabled by default. To save power, unused outputs should remain disabled. Outputs can be enabled at any time, except when the WM8751L is in OFF mode, as this may cause pop noise (see Minimising Pop Noise at the Analogue Outputs) REGISTER ADDRESS R26 (1Ah) Power Management (2) BIT 8 7 5 4 2 1 LABEL LOUT1 ROUT1 LOUT2 ROUT2 MONO OUT3 0 0 0 0 0 0 DEFAULT DESCRIPTION LOUT1 Enable ROUT1 Enable LOUT2 Enable ROUT2 Enable MONOOUT Enable OUT3 Enable
Note: All "Enable" bits are 1 = ON, 0 = OFF Table 10 Analogue Output Control
HEADPHONE SWITCH
The HPDETECT pin can be used as a headphone switch control input to automatically disable the speaker output and enable the headphone output e.g. when a headphone is plugged into a jack socket. In this mode, enabled by setting HPSWEN, HPDETECT switches between headphone and speaker outputs (typically, the pin is connected to a mechanical switch in the headphone socket to detect plug-in). The HPSWPOL bit reverses the pin's polarity. HPDETECT has CMOS thresholds at 0.3 AVDD / 0.7 AVDD. Note that the LOUT1, ROUT1, LOUT2 and ROUT2 bits in register 26 must also be set to enable headphone and speaker outputs (see tables below). REGISTER ADDRESS R24 (18h) Additional (1) BIT 6 LABEL HPSWEN 0 DEFAULT DESCRIPTION Headphone Switch Enable 0 : Headphone switch disabled 1 : Headphone switch enabled Headphone Switch Polarity 0 : HPDETECT high = headphone 1 : HPDETECT high = speaker
5
HPSWPOL
0
Table 11 Headphone Switch HPSWEN 0 0 0 0 1 1 1 1 1 1 1 1 HPSWPOL HPDETECT (PIN23) X X X X 0 0 0 0 1 1 1 1 X X X X 0 0 1 1 0 0 1 1 L/ROUT1 (reg. 26) 0 0 1 1 X X 0 1 X X 0 1 L/ROUT2 (reg. 26) 0 1 0 1 0 1 X X 0 1 X X Headphone enabled no no yes yes no no no yes no yes no no Speaker enabled no yes no yes no yes no no no no no yes
Table 12 Headphone Switch Operation
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AVDD ROUT1 LOUT1 47k / 100k HPDETECT
WM8751L
HPSWEN = 1 HPSWPOL = 1 L/ROUT1 = L/ROUT2 = 1 headphone / speaker switching
L R
+
Figure TBD Example Headset Detection circuit using normally-open switch
+
switch closes on insertion
HPSWEN = 1 HPSWPOL = 0 L/ROUT1 = L/ROUT2 = 1 headphone / speaker switching
AVDD ROUT1 LOUT1 47k / 100k HPDETECT
L switch opens on insertion
+
R
Figure TBD Example Headset Detection circuit using normally-closed switch
+
THERMAL SHUTDOWN
The speaker and headphone outputs can drive very large currents. To protect the WM8751L from overheating, a thermal shutdown circuit is included. If the device temperature reaches approximately 0 150 C and the thermal shutdown circuit is enabled (TSDEN = 1 ) then the speaker and headphone amplifiers (outputs OUT1L/R, OUT2L/R & OUT3) will be disabled. REGISTER ADDRESS R23 (17h) Additional (1) BIT 8 LABEL TSDEN 0 DEFAULT DESCRIPTION Thermal Shutdown Enable 0 : thermal shutdown disabled 1 : thermal shutdown enabled
Table 13 Thermal Shutdown
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WM8751L
LOUT1/ROUT1 OUTPUTS
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The LOUT1 and ROUT1 pins can drive a 16 or 32 headphone or a line output (see Headphone Output and Line Output sections, respectively). The signal volume on LOUT1 and ROUT1 can be independently adjusted under software control by writing to LOUT1VOL and ROUT1VOL, respectively. Note that gains over 0dB may cause clipping if the signal is large. Any gain setting below 0101111 (minimum gain) mutes the output driver. The corresponding output pin remains at the same DC level (the reference voltage on the VREF pin), so that no click noise is produced when muting or un-muting. The analogue outputs have a zero cross detect feature to minimize audible clicks and zipper noise when on gain changes (i.e. the updating of the gain value is delayed until the signal passes through zero). By default, this includes a time-out function, which forces the gain to update if no zero crossing occurs within a certain period of time. REGISTER ADDRESS R2 (02h) LOUT1 Volume BIT 6:0 LABEL LOUT1VOL DEFAULT 1111001 (0dB) DESCRIPTION LOUT1 Volume 1111111 = +6dB ... (80 steps) 0110000 = -67dB 0101111 to 0000000 = Analogue MUTE LOUT1 zero cross enable 1 = Change gain on zero cross only 0 = Change gain immediately Left Volume Update 0 = Store LOUT1VOL in intermediate latch (no gain change) 1 = Update left and right channel gains (left = LOUT1VOL, right = intermediate latch) ROUT1 Volume Similar to LOUT1VOL ROUT1 zero cross enable Similar to LO1ZC Right Volume Update 0 = Store ROUT1VOL in intermediate latch (no gain change) 1 = Update left and right channel gains (left = intermediate latch, right = ROUT1VOL) Time-out enable for zero-cross detectors 0 = time-out disabled (i.e. gains are never updated if there is no zero crossing) 1 = time-out enabled
7
LO1ZC
0
8
LO1VU
0
R3 (03h) ROUT1 Volume
6:0 7 8
ROUT1VOL RO1ZC RO1VU
1111001 0 0
R23 (17h)
0
TOEN
1
Table 14 LOUT1/ROUT1 Volume Control
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WM8751L
LOUT2/ROUT2 OUTPUTS
The LOUT2 and ROUT2 output pins are essentially similar to LOUT1 and ROUT1, but they are independently controlled and can also drive an 8 mono speaker. For speaker drive, the ROUT2 signal must be inverted (ROUT2INV = 1), so that the left and right channel are mixed to mono in the speaker [L-(-R) = L+R]. REGISTER ADDRESS R40 (28h) LOUT2 Volume BIT 6:0 7 LABEL LOUT2VOL LO2ZC DEFAULT 1111001 (0dB) 0 DESCRIPTION similar to LOUT1VOL Left zero cross enable 1 = Change gain on zero cross only 0 = Change gain immediately similar to LO1VU similar to ROUT1VOL Left zero cross enable 1 = Change gain on zero cross only 0 = Change gain immediately similar to RO1VU as for LOUT1 / ROUT1 ROUT2 Invert 0 = No Inversion (0 phase shift) 1 = Signal inverted (180 phase shift)
8 R41 (29h) ROUT2 Volume 6:0 7
LO2VU ROUT2VOL RO2ZC
0 1111001 (0dB) 0
8 R23 (17h) R24 (18h) Additional (2) 0 3
RO2VU TOEN ROUT2INV
0 1 0
Table 15 LOUT2/ROUT2 Control
MONO OUTPUT
The MONOOUT pin can drive a mono line output. The signal volume on MONOOUT can be adjusted under software control by writing to MONOOUTVOL. REGISTER ADDRESS R42 (2Ah) MONOOUT Volume BIT 6:0 LABEL MONOOUT VOL DEFAULT 1111001 (0dB) DESCRIPTION MONOOUT Volume 1111111 = +6dB ... (80 steps) 0110000 = -67dB 0101111 to 0000000 = Analogue MUTE MONOOUT zero cross enable 1 = Change gain on zero cross only 0 = Change gain immediately as for LOUT1 / ROUT1
7
MOZC
0
R23 (17h)
0
TOEN
1
Table 16 MONOOUT Volume Control
OUT3 OUTPUT
The OUT3 pin can drive a 16 or 32 headphone or a line output or be used as a DC reference for a headphone output. It can be selected to either drive out an inverted ROUT1 or inverted MONOOUT for e.g. an earpiece drive between OUT3 and LOUT1 or differential output between OUT3 and MONOOUT. OUT3SW selects the mode of operation required. REGISTER ADDRESS R24 (18h) Additional (2) BIT 8:7 LABEL OUT3SW DEFAULT 00 DESCRIPTION OUT3 select 00 : VREF 01 : ROUT1 10 : MONOOUT 11 : right mixer output
Table 17 OUT3 select
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WM8751L
DIGITAL AUDIO INTERFACE
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The digital audio interface is used for feeding audio data into the WM8751L. It uses three pins:
* * *
DACDAT: DAC data input DACLRC: DAC data alignment clock BCLK: Bit clock, for synchronisation
The clock signals BCLK and DACLRC can be outputs when the WM8751L operates as a master, or inputs when it is a slave (see Master and Slave Mode Operation, below). Four different audio data formats are supported:
* * * *
Left justified Right justified I 2S DSP mode
All four of these modes are MSB first. They are described in Audio Data Formats, below. Refer to the Electrical Characteristic section for timing information.
MASTER AND SLAVE MODE OPERATION
The WM8751L can be configured as either a master or slave mode device. As a master device the WM8751L generates BCLK and DACLRC and thus controls sequencing of the data transfer on DACDAT. In slave mode, the WM8751L responds with data to clocks it receives over the digital audio interface. The mode can be selected by writing to the MS control bit. Master and slave modes are illustrated below.
BCLK WM8751 DAC DACLRC DACDAT DSP / DECODER
BCLK WM8751 DAC DACLRC DACDAT DSP / DECODER
Figure 8 Master Mode
Figure 9 Slave Mode
AUDIO DATA FORMATS
In Left Justified mode, the MSB is available on the first rising edge of BCLK following a DACLRC transition. The other bits up to the LSB are then transmitted in order. Depending on word length, BCLK frequency and sample rate, there may be unused BCLK cycles before each DACLRC transition.
1/fs
LEFT CHANNEL DACLRC
RIGHT CHANNEL
BCLK
DACDAT
1
2
3
n-2 n-1
n
1
2
3
n-2 n-1
n
MSB
Input Word Length (WL)
LSB
MSB
LSB
Note: Input word length is defined by the WL register. Timing is shown with LRP = 1
Figure 10 Left Justified Audio Interface (assuming n-bit word length) In Right Justified mode, the LSB is available on the last rising edge of BCLK before a DACLRC transition. All other bits are transmitted before (MSB first). Depending on word length, BCLK frequency and sample rate, there may be unused BCLK cycles after each DACLRC transition.
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1/fs
WM8751L
LEFT CHANNEL DACLRC
RIGHT CHANNEL
BCLK
DACDAT
1
2
3
n-2 n-1
n
1
2
3
n-2 n-1
n
MSB
Data Word Length (WL)
LSB
MSB
LSB
Note: Word length is defined by the WL register. Timing is shown with LRP = 1
Figure 11 Right Justified Audio Interface (assuming n-bit word length) In I2S mode, the MSB is available on the second rising edge of BCLK following a DACLRC transition. The other bits up to the LSB are then transmitted in order. Depending on word length, BCLK frequency and sample rate, there may be unused BCLK cycles between the LSB of one sample and the MSB of the next.
1/fs
LEFT CHANNEL DACLRC
RIGHT CHANNEL
BCLK
1 BCLK 1 BCLK 3 n-2 n-1 n 1 2 3 n-2 n-1 n
DACDAT
1
2
MSB
Data Word Length (WL)
LSB
MSB
LSB
Note: Word length is defined by the WL register. Timing is shown with LRP = 1
Figure 12 I S Justified Audio Interface (assuming n-bit word length) In DSP mode, the left channel MSB is available on either the first or second rising edge of BCLK (selectable by LRP) following a rising edge of DACLRC. Right channel data immediately follows left channel data. Depending on word length, BCLK frequency and sample rate, there may be unused BCLK cycles between the LSB of the right channel data and the next sample.
1/fs 1 BCLK
2
DACLRC
BCLK
LEFT CHANNEL DACDAT
1 2 3 n-2 n-1 n 1 2
RIGHT CHANNEL
3 n-2 n-1 n
MSB
Data Word Length (WL)
LSB
Note: Word length is defined by the WL register. Timing is shown with LRP = 1
Figure 13 DSP Mode Audio Interface (Mode A; LRP = 0)
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WM8751L
1/fs 1 BCLK
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DACLRC/ ADCLRC
BCLK
LEFT CHANNEL DACDAT/ ADCDAT
1 2 3 n-2 n-1 n 1 2
RIGHT CHANNEL
3 n-2 n-1 n
MSB
Input Word Length (WL)
LSB
Figure 14 DSP Mode Audio Interface (Mode B; LRP = 1)
AUDIO INTERFACE CONTROL
The register bits controlling audio format, word length and master / slave mode are summarised below. REGISTER ADDRESS R7 (07h) Digital Audio Interface Format BIT 1:0 LABEL FORMAT DEFAULT 10 DESCRIPTION Audio Data Format Select 11 = DSP Mode 10 = I2S Format 01 = Left justified 00 = Right justified Audio Data Word Length 11 = 32 bits (see Note) 10 = 24 bits 01 = 20 bits 00 = 16 bits I2S, LJ, RJ Formats 1: Right Channel data when DACLRC high 0: Right Channel data when DACLRC low DSP Format 1: MSB available on 2nd BCLK rising edge after LRC rising edge 0: MSB available on 1st BCLK rising edge after LRC rising edge
3:2
WL
10
4
LRP
0
5
LRSWAP
0
Swap Left and Right Channels 0: No swap (L to L, R to R) 1: Swap (L to R, R to L) Master / Slave Mode Control 1: Master Mode 0: Slave Mode BCLK Invert 1: BCLK inverted 0: BCLK not inverted
6
MS
0
7
BCLKINV
0
Table 18 Audio Data Format Control Note: Right Justified mode does not support 32-bit data. If WL=11 in Right justified mode, the actual word length will be 24 bits.
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WM8751L
MASTER CLOCK AND AUDIO SAMPLE RATES
The WM8751L supports a wide range of master clock frequencies on the MCLK pin, and can generate many commonly used audio sample rates directly from the master clock. There are two clocking modes:
* *
`Normal' mode supports master clocks of 128fs, 192fs, 256fs, 384fs, and their multiples USB mode supports 12MHz or 24MHz master clocks. This mode is intended for use in systems with a USB interface, and eliminates the need for an external PLL to generate another clock frequency for the audio DAC.
REGISTER ADDRESS 6
BIT
LABEL MCLKDIV2 0
DEFAULT
DESCRIPTION Core Clock Divide by 2 0: Core clock = MCLK 1: Core clock = MCLK / 2 Sample Rate Control Clocking Mode Select 1: USB Mode 0: `Normal' Mode
5:1 0
SR [4:0] USB
0000 0
Table 19 Clocking and Sample Rate Control The clocking of the WM8751L is controlled using the MCLKDIV2, USB, and SR control bits. Setting the MCLKDIV2 bit divides MCLK by two internally. The USB bit selects between `Normal' and USB mode. Each combination of the SR4 to SR0 control bits selects one MCLK division ratio and hence one sample rate (see next page). The digital filter characteristics are automatically adjusted to suit the MCLK and sample rate selected (see Digital Filter Characteristics). Since all sample rates are generated by dividing MCLK, their accuracy depends on the accuracy of MCLK. If MCLK changes, the sample rates change proportionately. Note that some sample rates (e.g. 44.1kHz in USB mode) are approximated, i.e. they differ from their target value by a very small amount. This is not audible, as the maximum deviation is only 0.27% (8.0214kHz instead of 8kHz in USB mode - for comparison, a half-tone step corresponds to a 5.9% change in pitch).
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WM8751L
MCLK MCLKDIV2=0 12.288MHz MCLK MCLKDIV2=1 24.576MHz DAC SAMPLE RATE USB SR [4:0] FILTER TYPE 1 1 1 1 1 1 3 1 1 1 1 3 1 1 1 1 1 1 3 1 1 1 1 3 0 1 0 0 1 0 0 1 0 3 2
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BCLK (MS=1) MCLK/4 MCLK/4 MCLK/4 MCLK/4 MCLK/4 MCLK/4 MCLK/2 MCLK/4 MCLK/4 MCLK/4 MCLK/4 MCLK/2 MCLK/6 MCLK/6 MCLK/6 MCLK/6 MCLK/6 MCLK/6 MCLK/3 MCLK/6 MCLK/6 MCLK/6 MCLK/6 MCLK/3 MCLK MCLK MCLK MCLK MCLK MCLK MCLK MCLK MCLK MCLK MCLK
`Normal' Clock Mode (`*' indicates backward compatibility with WM8711 and WM8721) 8 kHz (MCLK/1536) 12 kHz (MCLK/1024) 16 kHz (MCLK/768) 24 kHz (MCLK/512) 32 kHz (MCLK/384) 48 kHz (MCLK/256) 96 kHz (MCLK/128) 11.2896MHz 22.5792MHz 8.0182 kHz (MCLK/1408) 11.025 kHz (MCLK/1024) 22.05 kHz (MCLK/512) 44.1 kHz (MCLK/256) 88.2 kHz (MCLK/128) 18.432MHz 36.864MHz 8 kHz (MCLK/2304) 12 kHz (MCLK/1536) 16 kHz (MCLK/1152) 24 kHz (MCLK/768) 32 kHz (MCLK/576) 48 kHz (MCLK/384) 96 kHz (MCLK/192) 16.9344MHz 33.8688MHz 8.0182 kHz (MCLK/2112) 11.025 kHz (MCLK/1536) 22.05 kHz (MCLK/768) 44.1 kHz (MCLK/384) 88.2 kHz (MCLK/192) 12.000MHz 24.000MHz 8 kHz (MCLK/1500) 11.0259 kHz (MCLK/1088) 12kHz (MCLK/1000) 16kHz (MCLK/750) 22.0588 kHz (MCLK/544) 24kHz (MCLK/500) 32 kHz (MCLK/375) 44.118 kHz (MCLK/272) 48 kHz (MCLK/250) 88.235kHz (MCLK/136) 96 kHz (MCLK/125) Table 20 Master Clock and Sample Rates 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 00010 * 01000 01010 11100 01100 * 00000 * 01110 * 10010 11000 11010 10000 * 11110 * 00011 * 01001 01011 11101 01101 * 00001 * 01111 * 10011 * 11001 11011 10001 * 11111 * 00010 * 11001 01000 01010 11011 11100 01100 * 10001 * 00000 * 11111 * 01110 *
USB Mode (`*' indicates backward compatibility with WM8711 and WM8721)
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WM8751L
SELECTION OF CONTROL MODE
The WM8751L is controlled by writing to registers through a serial control interface. A control word consists of 16 bits. The first 7 bits (B15 to B9) are address bits that select which control register is accessed. The remaining 9 bits (B8 to B0) are register bits, corresponding to the 9 bits in each control register. The control interface can operate as either a 3-wire or 2-wire MPU interface. The MODE pin selects the interface format. MODE Low High INTERFACE FORMAT 2 wire 3 wire
CONTROL INTERFACE
Table 21 Control Interface Mode Selection
3-WIRE SERIAL CONTROL MODE
In 3-wire mode, every rising edge of SCLK clocks in one data bit from the SDIN pin. A rising edge on CSB latches in a complete control word consisting of the last 16 bits.
latch CSB
SCLK
SDIN
B15
B14
B13
B12
B11
B10
B9
B8
B7
B6
B5
B4
B3
B2
B1
B0
control register address
control register data bits
Figure 15 3-Wire Serial Control Interface
2-WIRE SERIAL CONTROL MODE
The WM8751L supports software control via a 2-wire serial bus. Many devices can be controlled by the same bus, and each device has a unique 7-bit address (this is not the same as the 7-bit address of each register in the WM8751L). The WM8751L operates as a slave device only. The controller indicates the start of data transfer with a high to low transition on SDIN while SCLK remains high. This indicates that a device address and data will follow. All devices on the 2-wire bus respond to the start condition and shift in the next eight bits on SDIN (7-bit address + Read/Write bit, MSB first). If the device address received matches the address of the WM8751L and the R/W bit is `0', indicating a write, then the WM8751L responds by pulling SDIN low on the next clock pulse (ACK). If the address is not recognised or the R/W bit is `1', the WM8751L returns to the idle condition and wait for a new start condition and valid address. Once the WM8751L has acknowledged a correct address, the controller sends the first byte of control data (B15 to B8, i.e. the WM8751L register address plus the first bit of register data). The WM8751L then acknowledges the first data byte by pulling SDIN low for one clock pulse. The controller then sends the second byte of control data (B7 to B0, i.e. the remaining 8 bits of register data), and the WM8751L acknowledges again by pulling SDIN low. The transfer of data is complete when there is a low to high transition on SDIN while SCLK is high. After receiving a complete address and data sequence the WM8751L returns to the idle state and waits for another start condition. If a start or stop condition is detected out of sequence at any point during data transfer (i.e. SDIN changes while SCLK is high), the device jumps to the idle condition.
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WM8751L
SDIN DEVICE ADDRESS (7 BITS) RD / WR BIT ACK (LOW) CONTROL BYTE 1 (BITS 15 TO 8) ACK (LOW) CONTROL BYTE 1 (BITS 15 TO 8)
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ACK (LOW)
SCLK
START
register address and 1st register data bit
remaining 8 bits of register data
STOP
Figure 16 2-Wire Serial Control Interface
The WM8751L has two possible device addresses, which can be selected using the CSB pin. CSB STATE Low High DEVICE ADDRESS 0011010 0011011
Table 22 2-Wire MPU Interface Address Selection
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WM8751L
POWER SUPPLIES
The WM8751L can use up to four separate power supplies:
*
*
*
*
AVDD / AGND: Analogue supply, powers all analogue functions except the headphone drivers. AVDD can range from 1.8V to 3.6V and has the most significant impact on overall power consumption (except for power consumed in the headphone). A large AVDD slightly improves audio quality. HPVDD / HPGND: Headphone supply, powers the headphone drivers. HPVDD can range from 1.8V to 3.6V. HPVDD is normally tied to AVDD, but it requires separate layout and decoupling capacitors to curb harmonic distortion. With a larger HPVDD, louder headphone outputs can be achieved with lower distortion. If HPVDD is lower than AVDD, the output signal may be clipped. DCVDD: Digital core supply, powers all digital functions except the audio and control interfaces. DCVDD can range from 1.42V to 3.6V, and has no effect on audio quality. The return path for DCVDD is DGND, which is shared with DBVDD. DBVDD: Digital buffer supply, powers the audio and control interface buffers. This makes it possible to run the digital core at very low voltages, saving power, while interfacing to other digital devices using a higher voltage. DBVDD draws much less power than DCVDD, and has no effect on audio quality. The return path for DBVDD is DGND, which is shared with DCVDD.
It is possible to use the same supply voltage on all four. However, digital and analogue supplies should be routed and decoupled separately to keep digital switching noise out of the analogue signal paths.
POWER MANAGEMENT
The WM8751L has two control registers that allow users to select which functions are active. For minimum power consumption, unused functions should be disabled. To avoid any pop or click noise, it is important to enable or disable functions in the correct order (see Applications Information) REGISTER ADDRESS R25 (19h) Power Management (1) BIT 8:7 LABEL VMIDSEL DEFAULT 00 DESCRIPTION VMID resistor divider select 00 - VMID disabled 01 - 50k divider enabled 10 - 500k divider enabled VREF (necessary for all other functions) DAC Left DAC Right LOUT1 Output Buffer* ROUT1 Output Buffer* LOUT2 Output Buffer* ROUT2 Output Buffer* MONOOUT Output Buffer and Mono Mixer OUT3 Output Buffer
6 R26 (1Ah) Power Management (2) 8 7 6 5 4 3 2 1
VREF DACL DACR LOUT1 ROUT1 LOUT2 ROUT2 MOUT OUT3
0 0 0 0 0 0 0 0 0
Note: All control bits are 0=OFF, 1=ON * The left mixer is enabled when LOUT1=1 or LOUT2=1. The right mixer is enabled when ROUT1=1 or ROUT2=1. Table 23 Power Management
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WM8751L
STOPPING THE MASTER CLOCK
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In order to minimise power consumed in the digital core of the WM8751L, the master clock should be stopped in Standby and OFF modes. If this is cannot be done externally at the clock source, the DIGENB bit (R25, bit 0) can be set to stop the MCLK signal from propagating into the device core. However, since setting DIGENB has no effect on the power consumption of other system components external to the WM8751L, it is preferable to disable the master clock at its source wherever possible. REGISTER ADDRESS R25 (19h) Additional Control (1) 1 BIT LABEL DIGENB 0 DEFAULT DESCRIPTION Master clock disable 0: master clock enabled 1: master clock disabled
Table 2 ADC and DAC Oversampling Rate Selection NOTE: Before DIGENB can be set, the control bits DACL and DACR must be set to zero and a waiting time of 1ms must be observed. Any failure to follow this procedure may prevent DACs and ADCs from re-starting correctly.
SAVING POWER BY REDUCING OVERSAMPLING RATE
By default, the oversampling rate of the DAC digital filters is 128x. However, this can be changed to 64x by writing to the DACOSR bit. In the 64x oversampling mode, the digital filters consumes less power. However, the signal-to-noise ratio is slightly reduced. REGISTER ADDRESS R24 (18h) Additional Functions (2) 0 BIT LABEL DACOSR 0 DEFAULT DESCRIPTION DAC oversample rate select 1 = 64x (lowest power) 0 = 128x (best SNR)
Table 24 Oversampling Rate Selection
SAVING POWER AT LOW SUPPLY VOLTAGES
The analogue supplies to the WM8751L can run from 1.8V to 3.6V. By default, all analogue circuitry on the device is optimized to run at 3.3V. This set-up is also good for all other supply voltages down to 1.8V. However, at lower voltages, it is possible to save power by reducing the internal bias currents used in the analogue circuitry. This is controlled as shown below. REGISTER ADDRESS R23 (17h) Additional Control(1) BIT 7:6 LABEL VSEL[1:0] DEFAULT 11 DESCRIPTION Analogue Bias optimization 00 : Lowest bias current, optimized for 1.8V 01 : Low bias current, optimized for 2.5V 10, 11 : Default bias current, optimized for 3.3V
Table 25 Analogue Bias Selection
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WM8751L
REGISTER MAP
REGISTER ADDRESS (BIT 15 - 9) R0 (00h) R1 (01h) R2 (02h) R3 (03h) R4 (04h) R5 (05h) R6 (06h) R7 (07h) R8 (08h) 0000000 0000001 0000010 0000011 0000100 0000101 0000110 Reserved Reserved LOUT1 ROUT1 Reserved DAC Control Reserved 0 0 BCLKINV BCLK DIV2 R9 (09h) R10 (0Ah) R11 (0Bh) R12 (0Ch) R13 (0Dh) R14 (0Eh) R15 (0Fh) R16 - R22 R23 (17h) R24 (18h) R25 (19h) R26 (1Ah) R27 - R33 R34 (22h) R35 (23h) R36 (24h) R37 (25h) R38 (26h) R39 (27h) R40 (28h) R41 (29h) R42 (2Ah) 0100010 0100011 0100101 0100100 0100110 0100111 0101000 0101001 0101010 0010111 0011000 0011001 0011010 0001001 0001010 0001011 0001100 0001101 0001110 0001111 Reserved Left Gain Right Gain Bass Treble TBD Reset Reserved Additional (1) Additional (2) Pwr Mgmt (1) Pwr Mgmt (2) Reserved Left Mix (1) Left Mix (2) Right Mix (2) Right Mix (1) Mono Mix (1) Mono Mix (2) LOUT2 ROUT2 MONOOUT LD2LO RD2LO LD2RO RD2RO LD2MO RD2MO LO2VU RO2VU 0 LI2LO MI2LO MI2RO RI2RO LI2MO RI2MO LO2ZC RO2ZC MOZC LI2LOVOL MI2LOVOL MI2ROVOL RI2ROVOL LI2MOVOL RI2MOVOL TSDEN OUT3SW VMIDSEL DACL DACR VSEL LDVU RDVU 0 0 BB 0 BC TC MS MCLK DIV2 000000000 LDACVOL (Right DAC Digital Volume) RDACVOL (Right DAC Digital Volume) 0 0 0 0 000000000 writing 000000000 to this register resets all registers to their default state 000000 DMONOMIX 0 HPZC 0 ROUT2 0 0 0 MOUT DACINV 0 0 OUT3 TOEN DACOSR DIGENB 0 BASS (Bass Intensity) TRBL (Treble Intensity) LRSWAP 0 DAT 0 0 LO1VU RO1VU LO1ZC RO1ZC 000000000 0 000000000 LRP SR WL FORMAT USB DACMU DEEMPH 0 000000000 000000000 LOUT1VOL ROUT1VOL REMARKS BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0
0000111 Audio Interface 0001000 Clocking
HPSWEN HPSWPOL ROUT2INV VREF LOUT1 0 ROUT1 0 LOUT2 000000
0 0 0 0 0 0 LOUT2VOL ROUT2VOL ROUT2VOL
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 DMEN 0
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WM8751L DIGITAL FILTER CHARACTERISTICS
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Depending on the MCLK frequency and sample rate selected, 4 different types of digital filter can be used in the DAC, called Type 0, 1, 2 and 3 (see "Master Clock and Audio Sample Rates"). The performance of Types 0 and 1 is listed in the table below, the responses of all filters is shown in the following pages. PARAMETER Passband Passband Ripple Stopband Stopband Attenuation Passband Passband Ripple Stopband Stopband Attenuation Table 26 Digital Filter Characteristics f > 0.5465fs 0.5465fs -50 dB f > 0.584fs +/- 0.03dB -6dB 0.584fs -50 0 0.5fs +/- 0.03 dB 0.4535fs dB TEST CONDITIONS +/- 0.03dB -6dB MIN 0 0.5fs +/-0.03 dB TYP MAX 0.416fs UNIT
DAC Filter Type 0 (USB mode, 250fs operation)
DAC Filter Type 1 (USB mode, 272fs or Normal mode operation)
TERMINOLOGY
1. 2. Stop Band Attenuation (dB) - the degree to which the frequency spectrum is attenuated (outside audio band) Pass-band Ripple - any variation of the frequency response in the pass-band region
DAC FILTER RESPONSES
0.02
0
0.01
-20
0
Response (dB)
-40
Response (dB)
0 0.5 1 1.5 Frequency (Fs) 2 2.5 3
-0.01 -0.02 -0.03 -0.04 -0.05
-60
-80
-100
-0.06 0 0.05 0.1 0.15 0.2 0.25 0.3 Frequency (Fs) 0.35 0.4 0.45 0.5
Figure 17 DAC Filter Frequency Response - Type 0
Figure 18 DAC Filter Ripple - Type 0
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0.02
WM8751L
0.01
0
-20
0
Response (dB)
-40
Response (dB)
-0.01 -0.02 -0.03 -0.04
-60
-80
-0.05
-100 0 0.5 1 1.5 Frequency (Fs) 2 2.5 3
-0.06 0 0.05 0.1 0.15 0.2 0.25 0.3 Frequency (Fs) 0.35 0.4 0.45 0.5
Figure 19 DAC Filter Frequency Response - Type 1
Figure 20 DAC Filter Ripple - Type 1
0.02
0
0.01
-20
0
Response (dB)
-40
Response (dB)
-0.01 -0.02 -0.03 -0.04
-60
-80
-0.05
-100 0 0.5 1 1.5 Frequency (Fs) 2 2.5 3
-0.06 0 0.05 0.1 0.15 Frequency (Fs) 0.2 0.25
Figure 21 DAC Filter Frequency Response - Type 2
Figure 22 DAC Filter Ripple - Type 2
0
0
-0.05
-20
Response (dB)
Response (dB)
-40
-0.1
-60
-0.15
-80
-0.2
-100 0 0.5 1 1.5 Frequency (Fs) 2 2.5 3
-0.25 0 0.05 0.1 0.15 Frequency (Fs) 0.2 0.25
Figure 23 DAC Filter Frequency Response - Type 3
Figure 24 DAC Filter Ripple - Type 3
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WM8751L PACKAGE DIMENSIONS
FL: 32 PIN QFN PLASTIC PACKAGE 5 X 5 X 0.9 mm BODY, 0.50 mm LEAD PITCH
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DM030.C
CORNER TIE BAR 5 25
D2 B D2/2 32
SEE DETAIL A
D
L 24 1 INDEX AREA (D/2 X E/2) E2/2
A
E2
SEE DETAIL B
E
17
8 2X 16 e 15 B 9 b 2X aaa C aaa C
TOP VIEW
ccc C (A3) 1 A 0.08 C A1 SEATING PLANE 1 e/2 TERMINAL TIP L 1
DETAIL A
32x b bbb M C A B
CORNER TIE BAR 5
C
0.
DETAIL B
DATUM
43 m m 6 56 0.
32x K
m m
EXPOSED CENTRE PAD
R
e
1 L1 L1 R
Symbols A A1 A3 b D D2 E E2 e L L1 R K aaa bbb ccc REF: MIN 0.85 0 0.18 4.90 3.2 4.90 3.2 0.35
1 b(min)/2 0.20 Tolerances of Form and Position 0.15 0.10 0.10 JEDEC, MO-220, VARIATION VKKD-2
Dimensions (mm) NOM MAX 0.90 1.00 0.02 0.05 0.2 REF 0.23 0.30 5.00 5.10 3.3 3.4 5.00 5.10 3.3 3.4 0.5 BSC 0.4 0.45 0.1
NOTE
1 2 2
NOTES: 1. DIMENSION b APPLIED TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm FROM TERMINAL TIP. DIMENSION L1 REPRESENTS TERMINAL PULL BACK FROM PACKAGE SIDE WALL. MAXIMUM OF 0.1mm IS ACCEPTABLE. WHERE TERMINAL PULL BACK EXISTS, ONLY UPPER HALF OF LEAD IS VISIBLE ON PACKAGE SIDE WALL DUE TO HALF ETCHING OF LEADFRAME. 2. FALLS WITHIN JEDEC, MO-220 WITH THE EXCEPTION OF D2, E2: D2,E2: LARGER PAD SIZE CHOSEN WHICH IS JUST OUTSIDE JEDEC SPECIFICATION 3. ALL DIMENSIONS ARE IN MILLIMETRES 4. THIS DRAWING IS SUBJECT TO CHANGE WITHOUT NOTICE. 5. SHAPE AND SIZE OF CORNER TIE BAR MAY VARY WITH PACKAGE TERMINAL COUNT. CORNER TIE BAR IS CONNECTED TO EXPOSED PAD INTERNALLY
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WM8751L
APPLICATIONS INFORMATION
MINIMISING POP NOISE AT THE ANALOGUE OUTPUTS
To minimise any pop or click noise when the system is powered up or down, the following procedures are recommended.
POWER UP
* * * * * * * * *
Switch on power supplies. By default the WM8751L is in OFF Mode (i.e. only the control interface is powered up) Enable the reference voltage VREF by setting the WM8751L to Standby mode. DO NOT enable any of the analogue outputs at this point. Allow VREF to settle. The settling time depends on the value of the capacitor connected at VMID (formula TBD). Enable outputs, DACs, etc. (sequence TBD) Set ACTIVE = 1 to enable the Audio Interface Set DACMU = 0 to soft-un-mute the audio DACs.
POWER DOWN
Set DACMU = 1 to soft-mute the audio DACs. Disable functions (sequence TBD) Switch off the power supplies.
LINE OUTPUT CONFIGURATION
All the analogue outputs, LOUT1/ROUT1, LOUT2/ROUT2, and MONOOUT, can be used as line outputs. Recommended external components are shown below.
C1 1uF LOUT2 R1 100 Ohm LINE-OUT SOCKET (LEFT) AGND
WM8751L
ROUT2 C2 1uF R2 100 Ohm
LINE-OUT SOCKET (RIGHT) AGND
Figure 25 Recommended Circuit for Line Output The DC blocking capacitors and the load resistance together determine the lower cut-off frequency, fc. Assuming a 10 kOhm load and C1, C2 = 10F: fc = 1 / 2 (RL+R1) C1 = 1 / (2 x 10.1k x 1F) = 16 Hz Increasing the capacitance lowers fc, improving the bass response. Smaller values of C1 and C2 will diminish the bass response. The function of R1 and R2 is to protect the line outputs from damage when used improperly.
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WM8751L
HEADPHONE OUTPUT CONFIGURATION
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The analogue outputs LOUT1/ROUT1, LOUT2/ROUT2, and OUT3 can drive a 16 or 32 headphone load, either through DC blocking capacitors, or DC coupled without any capacitor.
Headphone Output using DC blocking capacitors
C1 220uF
DC Coupled Headphone Output (OUT3SW = 00)
LOUT1 ROUT1 WM8751L
LOUT1 WM8751L
C2 220uF
HPDCEN = 1
ROUT1 HPDC = AVDD/2
HPGND = 0V
Figure 26 Recommended Headphone Output Configurations When DC blocking capacitors are used, then their capacitance and the load resistance together determine the lower cut-off frequency, fc. Increasing the capacitance lowers fc, improving the bass response. Smaller capacitance values will diminish the bass response. Assuming a 16 Ohm load and C1 = 220F: fc = 1 / 2 RLC1 = 1 / (2 x 16 x 220F) = 45 Hz In the DC coupled configuration, the headphone "ground" is connected to the OUT3 pin, which must be enabled by setting O3 = 1 and OUT3SW = 00. As the OUT3 pin produces a DC voltage of AVDD/2 (=VREF), there is no DC offset between LOUT1/ROUT1 and OUT3, and therefore no DC blocking capacitors are required. This saves space and material cost in portable applications. It is recommended to connect the DC coupled headphone outputs only to headphones, and not to the line input of another device. Although the built-in short circuit protection will prevent any damage to the headphone outputs, such a connection may be noisy, and may not function properly if the other device is grounded.
SPEAKER OUTPUT CONFIGURATION
LOUT2 and ROUT2 can differentially drive a mono 8 speaker as shown below.
LEFT MIXER
LOUT2
WM8751L
ROUT2INV = 1 -1
LOUT2VOL
VSPKR = L-(-R) = L+R
ROUT2
RIGHT MIXER
ROUT2VOL
Figure 27 Speaker Output Connection The right channel is inverted by setting the ROUT2INV bit, so that the signal across the loudspeaker is the sum of left and right channels.
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WM8751L
IMPORTANT NOTICE
Wolfson Microelectronics Ltd (WM) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current. All products are sold subject to the WM terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability.
WM warrants performance of its products to the specifications applicable at the time of sale in accordance with WM's standard warranty. Testing and other quality control techniques are utilised to the extent WM deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements.
In order to minimise risks associated with customer applications, adequate design and operating safeguards must be used by the customer to minimise inherent or procedural hazards.
WM assumes no liability for applications assistance or customer product design. WM does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of WM covering or relating to any combination, machine, or process in which such products or services might be or are used. WM's publication of information regarding any third party's products or services does not constitute WM's approval, license, warranty or endorsement thereof.
Reproduction of information from the WM web site or datasheets is permissable only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations and notices. Representation or reproduction of this information with alteration voids all warranties provided for an associated WM product or service, is an unfair and deceptive business practice, and WM is not responsible nor liable for any such use.
Resale of WM's products or services with statements different from or beyond the parameters stated by WM for that product or service voids all express and any implied warranties for the associated WM product or service, is an unfair and deceptive business practice, and WM is not responsible nor liable for any such use.
ADDRESS:
Wolfson Microelectronics Ltd 20 Bernard Terrace Edinburgh EH8 9NX United Kingdom
Tel :: +44 (0)131 272 7000 Fax :: +44 (0)131 272 7001 Email :: sales@wolfsonmicro.com
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