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19-1743; Rev 1; 2/01
Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator
General Description
The MAX4298 and MAX4299 are audio system ICs designed for single +5V applications. The MAX4299 features a stereo headphone driver, a microphone amplifier, and a +3.3V linear regulator; the MAX4298 features the stereo headphone driver only. The MAX4298/ MAX4299 are designed specifically for harsh digital environments where board space is at a premium and the digital power supply is noisy. The design uses innovative design techniques to achieve ultra-high power-supply rejection across the audio signal band while, at the same time, delivering a high-current Railto-Rail(R) output drive capability. The chip is designed to drive highly capacitive loads that may be encountered when driving long cables to a remote load such as desktop/notebook headphones or speakers. These devices are fully compliant with PC99 standards. The amplifiers exhibit 115dB of DC power-supply rejection and 80dB at 100kHz. The output amplifiers are capable of driving a 1.5VRMS signal into a 10k load with 0.0008% THD+N. They can also drive 32 headphones to 1.2VRMS with 0.02% distortion. At +3.3V, the linear regulator can output 100mA of current. The MAX4298 is available in a tiny 10-pin MAX while the MAX4299 is available in the space-saving 16-pin TSSOP package.
Features
o Audio System IC (MAX4299) Ultra-High PSRR Stereo Headphone Driver Ultra-High PSRR Microphone Amp 100mA, 3.3V Linear Regulator o 93dB typ PSRR at 20kHz Operates Directly from Noisy Digital Supplies o Clickless/Popless Power-Up, Power-Down, Mute and Unmute o PC99-Compliant Output Drivers: Better than 1VRMS Output into 16 Load and 1.5VRMS and 0.0008% THD+N into 10k Load o PC99-Compliant Microphone Amplifier: 0.005% THD+N into 10k Load o 22nF Capacitive Load Drive Capability o 4.5V to 5.5V Single-Supply Operation o Internally Generated Bias Voltage o All Gains Externally Adjustable o Available in Space-Saving Packages 10-Pin MAX (MAX4298) 16-Pin TSSOP (MAX4299)
MAX4298/MAX4299
________________________Applications
Notebook and Desktop Audio Hands-Free Headsets USB Audio Peripherals IP Telephones Wireless Internet Devices MP3 Players/Recorders
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
PART MAX4298EUB MAX4298ESD MAX4299EWP MAX4299EUE
Ordering Information
TEMP. RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 10 MAX 14 SO 20 SO 16 TSSOP
Typical Operating Circuit appears at end of data sheet.
PSRR vs. Frequency
MAX4298/9-13
Pin Configurations
TOP VIEW
OUT1 1 GND IN1 BIAS SVCC 2 3 4 5 10 VCC 9 OUT2 IN2 CBYPASS MUTE
-50 -60 -70 -80 PSRR (dB) -90 -100 -110 -120 -130 -140 -150 100 1k 10k
MAX4298
8 7 6
100k
MAX Pin Configurations continued at end of data sheet. 1
FREQUENCY (Hz)
________________________________________________________________ Maxim Integrated Products
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator MAX4298/MAX4299
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC) to GND ...............................................+6V Standby Supply Voltage (SVCC) to GND ...............................+6V REG, FB, REGON to GND ..........................-0.3V to (VCC + 0.3V) BIAS, CBYPASS, MUTE, IN_, MICIN to GND ..............-0.3V to the Larger of (VCC +0.3V) or (SVCC +0.3V) OUT_, MICOUT to GND ................................-0.3V to the Smaller of +5.5V, or (VCC + 0.3V) Duration of Output Short-Circuit to GND or VCC ................10min Continuous Power Dissipation 10-Pin MAX (derate 5.6mW/C above +70C) ...........444mW 14-Pin SO (derate 8.3mW/C above +70C)................667mW 20-Pin SO (derate 10.0mW/C above +70C)..............800mW 16-Pin TSSOP (derate 9.4mW/C above +70C) .........755mW Operating Temperature Range ..........................-40C to +85C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = SVCC = +5V, RL = on all outputs, CBYPASS = 1F, CBIAS = 1F, CREG = 10F (MAX4299), TA = TMIN to TMAX, unless otherwise noted. Load resistors (RL) are terminated to 2.25V. Typical values are at TA = +25C. Specifications apply to both MAX4298 and MAX4299, unless otherwise noted.) (Note 1)
PARAMETER Supply Voltage Range Quiescent Current Mute Quiescent Current SVCC Current (Note 2) DRIVER AMPLIFIERS Input Offset Voltage Input Bias Current Power-Supply Rejection Ratio VOS IBIAS DC, VCC = 4.5V to 5.5V PSRR f = 20kHz f = 100kHz RL = 10k Output Drive VOUT RL = 32 RL = 16 AV = -1V/V, f = 1kHz, RL = 10k, VOUT = 1.5VRMS THD + Noise AV = -1V/V, f = 1kHz, RL = 32, VOUT = 1.2VRMS, (Notes 3, 4) AV = -1V/V, f = 1kHz, RL = 16, VOUT = 1.0VRMS Full-Scale Signal-to-Noise Ratio (Note 4) Capacitive Drive Open-Loop Voltage Gain Unity-Gain Bandwidth AVOL GBW RL = 32, 0.55V VOUT VCC - 0.55V 76 SNR RL = 10k, VOUT = 1.06VRMS, AV = -1V/V 1.45 1.2 1.0 1 0.2 115 93 80 1.59 1.53 1.48 0.0008 0.02 0.04 105 22 87 1.3 dB nF dB MHz 0.1 % VRMS dB 10 mV nA ISVCC SYMBOL VCC ICC MAX4298 MAX4299 MAX4298 MAX4299 VBIAS = 1.125V, VCC = 0 VBIAS = 2.25V, VCC = 5.0V CONDITIONS Inferred from PSRR test MIN 4.5 10.2 10.6 10.2 10.6 300 7 TYP MAX 5.5 17.5 18.0 17.5 18.0 500 UNITS V mA mA A
2
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Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator MAX4298/MAX4299
ELECTRICAL CHARACTERISTICS (continued)
(VCC = SVCC = +5V, RL = on all outputs, CBYPASS = 1F, CBIAS = 1F, CREG = 10F (MAX4299), TA = TMIN to TMAX, unless otherwise noted. Load resistors (RL) are terminated to 2.25V. Typical values are at TA = +25C. Specifications apply to both MAX4298 and MAX4299, unless otherwise noted.) (Note 1)
PARAMETER BIAS VOLTAGE OUTPUT DC BIAS Voltage Line Regulation Load Regulation Input Voltage High Input Voltage Low Input Leakage Current Input Offset Voltage Input Bias Current Power-Supply Rejection Ratio Voltage Gain Output Drive THD + Noise (Note 4) Full-Scale Signal-to-Noise Ratio (Note 4) All-Hostile Crosstalk Unity Gain Bandwidth REGULATOR (MAX4299 only) Regulator Output Voltage Line Regulation Load Regulation FB Voltage VFB VREG VCC = 4.5V to 5.5V. IL = 0 to 100mA, using internal feedback VCC = 4.5V to 5.5V, IL = 50mA IL = 10mA to 100mA IL = 0 to 100mA Reference for regulator adjustment 3.15 3.3 0.2 30 50 1.233 3.45 V mV mV mV V GBW VINH VINL IIN VOS IBIAS DC, VCC = 4.5V to 5.5V PSRR AVOL VOUT THD+N SNR f = 20kHz f = 100kHz RL = 10k, 0.13V VMICOUT VCC - 0.13V RL = 10k f = 1kHz, RL = 10k, VMICOUT = 1.5VRMS AV = -1V/V AV = -10V/V 80 1.4 VIN = 0 or VCC 2 0.2 115 93 80 100 1.58 0.005 0.03 80 80 1 dB VRMS % dB dB MHz dB IL = 0 to 1A 2.4 0.8 1 10 DIGITAL INPUTS (MUTE for MAX4298/MAX4299, and REGON for MAX4299) V V A mV nA VBIAS IL = 0 2.13 2.25 120 50 2.37 V dB mV SYMBOL CONDITIONS MIN TYP MAX UNITS
MICROPHONE AMPLIFIER (MAX4299 only)
RL = 10k, VMICOUT = 1.06VRMS, AV = -10V/V f = 10kHz (Note 5)
Note 1: Note 2: Note 3: Note 4: Note 5:
All devices are 100% production tested at TA = +25C. All temperature limits are guaranteed by design. Current drawn from SVCC when VCC < 4V. Guaranteed by design. Measurement bandwidth is 20Hz to 22kHz. Voltage at MICOUT with OUT1 = OUT2 = 1VRMS into 32.
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3
Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator MAX4298/MAX4299
Typical Operating Characteristics
(VCC = SVCC = +5V, typical operating circuit, TA = +25C, unless otherwise noted.)
MAX4298 SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX4298/99-01
POWER-UP/POWER-DOWN
MAX4298/9-02
MUTE PERFORMANCE
OUT 3 OUTPUT VOLTAGE (V) 2 1 0 -1 SPEAKER -2 RL = 32 CAC = 220F 1.5 2.0
MAX4298/9-03
11.5 11.0 10.5 ICC (mA) 10.0 9.5 TA = -40C 9.0 8.5 4.2 4.4 4.6 4.8 5.0 5.2 5.4 TA = +85C
2.5 RL = 32 2.0 OUTPUT VOLTAGE (V) OUT 1.5 1.0 0.5 0 -0.5 SPEAKER
4
TA = +25C
5.6
0
1.0 TIME (s)
2.0
0
0.5
1.0 TIME (s)
VCC (V)
POWER-DOWN/POWER-UP with SCHOTTKY DIODE AND RESERVOIR CAPACITOR
VCC = 0 VCC = 5V SVCC THD+N (%)
MAX4298/99-04
DRIVER OUT THD+N vs. FREQUENCY
MAX4298/99-05
DRIVER OUT THD+N vs. FREQUENCY
MAX4298/99-06
6 5 4 VOLTAGE (V) 3 2 1 0 -1 0 0.5 1.0 TIME (s) RL = 32 CAC = 22OF 1.5 VOUT
1
1
0.1 THD+N (%)
0.1
BW = 80kHz BW = 22kHz
0.01
BW = 80kHz BW = 22kHz
0.01
0.001 RL = 10k AV = -1 VOUT = 1.5VRMS 100 1k 10k 100k
0.001
0.0001
0.0001 100 1k
RL = 32 AV = -1 VOUT = 1.2VRMS 10k 100k
2.0
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
DRIVER OUT THD+N vs. FREQUENCY
MAX4298/99-07
DRIVER OUT THD+N vs. AMPLITUDE
MAX4298/99toc08
DRIVER OUT THD+N vs. AMPLITUDE
BW = 22kHz 1 fIN = 1kHz
MAX4298/99toc09
1
10
BW = 22kHz
10
0.1 THD+N (%)
BW = 80kHz BW = 22kHz THD+N (%)
1
0.01
0.01
THD+N (%) AV = -1 RL = 10k
0.1
0.1
0.01
0.001
0.0001 100 1k
RL = 16 AV = -1 VOUT = 1VRMS 10k 100k
0.001 fIN = 1kHz 0.0001 0 0.5 1
0.001 0.0001 1.5 2 0 0.5 1 OUTPUT VOLTAGE (VRMS) OUTPUT VOLTAGE (VRMS) RL = 32 AV = -1 1.5 2
INPUT FREQUENCY (Hz)
4
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Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator MAX4298/MAX4299
Typical Operating Characteristics (continued)
(VCC = SVCC = +5V, typical operating circuit, TA = +25C, unless otherwise noted.)
DRIVER OUT CHANNEL SEPARATION vs. INPUT FREQUENCY
MAX4298/99toc10 MAX4298/9-11
DRIVER OUT THD+N vs. AMPLITUDE
10 -60 -70 CHANNEL SEPARATION (dB) BW = 22kHz
DRIVER OUT MUTED OUTPUT ATTENUATION vs. INPUT FREQUENCY
-85 -90 -95 -100 -105 -110 -115 -120 100 1k RL = 16 A = RI = 20k, RF = 20k B = RI = 10k, RF = 10k C = RI = 10k, RF = 20k 10k 100k B C A
MAX4298/9-12
-80 MUTED OUTPUT ATTENUATION (dB)
1 fIN = 1kHz THD+N (%) 0.1
OUT2 TO OUT1 -80 -90 -100 -110 -120
0.01
OUT1 TO OUT2 RL = 10k AV = -1 VOUT = 1VRMS 100 1k 10k 100k
0.001 0.0001 0 0.5 1 OUTPUT VOLTAGE (VRMS) RL = 16 AV = -1 1.5 2
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
DRIVER OUT POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
MAX4298/9-13
DRIVER OUT OPEN-LOOP FREQUENCY RESPONSE
90 80 70 60 GAIN (dB) 50 40 30 20 10 0 32 || 15pF 0.1 1 10 100 GAIN PHASE
MAX4298/9-14
DRIVER OUT OPEN-LOOP FREQUENCY RESPONSE
200 180 160 140 PHASE (deg) GAIN (dB) 120 100 80 60 40 20 90 80 70 60 50 40 30 20 10 0 -10 0.01 32 || 1.5nF 0.1 1 10 100 GAIN PHASE
MAX4298/9-15
-50 -60 -70 -80 PSRR (dB) -90 -100 -110 -120 -130 -140 -150 100 1k 10k
200 180 160 140 PHASE (deg) PHASE (deg) 120 100 80 60 40 20
100k
-10 0.01
0 1000 10,000
0 1000 10,000
FREQUENCY (Hz)
INPUT FREQUENCY (kHz)
INPUT FREQUENCY (kHz)
DRIVER OUT OPEN-LOOP FREQUENCY RESPONSE
90 80 70 60 GAIN (dB) 50 40 30 20 10 0 -10 0.01 32k || 22nF 0.1 1 10 100 GAIN PHASE
MAX4298/9-16
DRIVER OUT OPEN-LOOP FREQUENCY RESPONSE
200 180 160 140 PHASE (deg) GAIN (dB) 120 100 80 60 40 20 90 80 70 60 50 40 30 20 10 0 -10 0.01 10k || 15pF 0.1 1 10 100 GAIN PHASE
MAX4298/9-17
DRIVER OUT OPEN-LOOP FREQUENCY RESPONSE
200 180 160 140 PHASE (deg) GAIN (dB) 120 100 80 60 40 20 90 80 70 60 50 40 30 20 10 0 -10 0.01 10k || 1.5nF 0.1 1 10 100 GAIN PHASE
MAX4298/9-18
200 180 160 140 120 100 80 60 40 20
0 1000 10,000
0 1000 10,000
0 1000 10,000
INPUT FREQUENCY (kHz)
INPUT FREQUENCY (kHz)
INPUT FREQUENCY (kHz)
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5
Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator MAX4298/MAX4299
Typical Operating Characteristics (continued)
(VCC = SVCC = +5V, typical operating circuit, TA = +25C, unless otherwise noted.)
DRIVER OUT OPEN-LOOP FREQUENCY RESPONSE
90 80 70 60 GAIN (dB) 50 40 30 20 10 0 -10 0.01 10k || 22nF 0.1 1 10 100 GAIN PHASE
MAX4298/99 toc19
MICOUT ALL HOSTILE CROSSTLAK (INPUT REFERRED)
AV = -100
MAX4298/99 toc20
MICOUT OPEN LOOP FREQUENCY RESPONSE
90 80 70 60 GAIN (dB)
MAX4298/99 toc21
200 180 ALL HOSTILE CROSSTALK (dB) 160 140 PHASE (deg) 120 100 80 60 40 20
-20
200 180 160 140 PHASE (deg) 120
-40
-60
50 40 30 20 10 0 10k || 15pF -10 0.01 0.1 1 GAIN PHASE
100 80 60 40 20
-80
-100 -120 0.01
0 1000 10,000
0.1
1
10
100
10
100
0 1000 10,000
INPUT FREQUENCY (kHz)
INPUT FREQUENCY (kHz)
INPUT FREQUENCY (kHz)
MICOUT OPEN LOOP FREQUENCY RESPONSE
90 80 70 60 GAIN (dB) 50 40 30 20 10 0 10k || 150pF -10 0.01 0.1 1 GAIN PHASE
MAX4298/99 toc22
MICOUT THD+N vs. AMPLITUDE
MAX4298/99 toc23
REGOUT OUTPUT VOLTAGE vs. LOAD CURRENT
MAX4298/99 toc24
200 180 160 140 THD+N (%) 120 100 80 60 40
10
3.5
1
3.4 OUTPUT VOLTAGE (V)
0.1
3.3
0.01 RL = 10k AV = -1 fIN = 1kHz BW = 22kHz 0 0.5 1.0 AMPLITUDE (VRMS) 1.5 2.0
3.2
0.001 0.0001
3.1
10
100
20 0 1000 10,000
3.0 0 20 40 60 80 100 LOAD CURRENT (mA)
INPUT FREQUENCY (kHz)
REGOUT TRANSIENT RESPONSE
MAX4298/99 toc25
REGOUT TRANSIENT RESPONSE
MAX4298/99 toc26
VOUT 30mV/div
VOUT 30mV/div
100mA IL 0
100mA IL 10mA
200s/div
200s/div
6
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Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator
Pin Description
PIN MAX4298 10-PIN MAX -- MAX4298 14-PIN SO -- MAX4299 16-PIN TSSOP 16 MAX4299 20-PIN SO 1 REG Regulator Output. Bypass REG to GND with a 10F capacitor. Regulator Feedback. Internal resistors from this point to REG and GND define the regulator output value. Adjustments can be made to the output value by adding resistors in the same place externally. Driver Amplifier Output Power Ground for Driver Outputs Ground Inverting Input for Driver Amplifier Bias Point for Amplifiers. Bypass BIAS to GND with a 1F capacitor. Standby Power Supply. Connect to a standby +5V supply that is always on, or bypass with 220F and connect a Schottky diode from VCC to SVCC. Short to VCC if clickless power-down is not essential. Microphone Amplifier Output Inverting Input for Microphone Amplifier Mute Digital Input. Connect to GND for normal operation. When MUTE is connected to VCC, OUT1 and OUT2 are muted, REG stays on, and MICOUT stays on. Bypass to GND with a 1F Capacitor Inverting Input for Driver Amplifier Driver Amplifier Output Power Supply. Connect to +5V. No Connection. Not internally connected. Regulator Control. Connect to VCC for normal operation. Connect to GND to shut off the regulator. NAME FUNCTION
MAX4298/MAX4299
--
--
1
2
FB
1 -- 2 3 4
2 -- 3 4 5
2 3 4 5 6
4 5 6 7 8
OUT1 PGND GND IN1 BIAS
5
6
7
9
SVCC
-- --
-- --
8 9
10 11
MICOUT MICIN
6
9
10
13
MUTE
7 8 9 10 -- --
10 11 12 13 1, 7, 8, 14 --
11 12 13 14 -- 15
14 15 16 17 3, 12, 18, 19 20
CBYPASS IN2 OUT2 VCC N.C. REGON
Detailed Description
The MAX4298/MAX4299 are audio system ICs designed for single +5V applications. The MAX4299 has a stereo headphone driver, a microphone amplifier, and a 100mA +3.3V linear regulator; the MAX4298 has the stereo headphone driver only. The MAX4298/MAX4299 are designed specifically for harsh digital environments where board space is at a premium and the digital
power supply is noisy. The design uses innovative design techniques to achieve ultra-high power-supply rejection across the audio signal band while, at the same time, delivering a high current rail-to-rail output drive capability. These devices are designed to drive highly capacitive loads that may be encountered when driving long cables to a remote load such as desktop/notebook headphones or speakers. They are fully compliant to PC99 standards. Figure 1 is the
7
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Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator MAX4298/MAX4299
VCC
VCC REG + _ 18.4k FB 11k 1.233V SVCC REGON
MAX4298
SVCC _ + 50k 2.25V + _ CBYPASS
IN1 BIAS IN2
OUT1 MUTE
MAX4299
OUT2
IN1 _ + BIAS 50k 2.25V + _ OUT2 N.C. + _ MICIN GND PGND OUT1
GND
Figure 1. MAX4298 Block Diagram
IN2
MUTE
MAX4298 block diagram and Figure 2 is the MAX4299 block diagram. The amplifiers exhibit better than 115dB of DC powersupply rejection and 93dB at 20kHz. The output amplifiers are capable of driving a 1.5VRMS signal into 10k load with 0.0008% distortion. They can also drive 32 headphones to 1.2V RMS with 0.02% distortion. At +3.3V, the linear regulator can output 100mA of current.
MICOUT CBYPASS
Figure 2. MAX4299 Block Diagram
BIAS
The common-mode bias point for the amplifiers is set to 2.25V by internal circuitry that has two functions. It provides a clickless/popless power-up/power-down waveform for the amplifiers. Also, it generates a groundreferenced bias voltage with ultra-high power-supply rejection ratio (PSRR). BIAS should be bypassed with 1F to GND.The output impedance of the BIAS pin is 50k.
and OUT2 are muted, but remain in a low-impedance state to ensure clickless/popless operation.
Clickless/Popless Function
The MAX4298/MAX4299 are designed for high-fidelity audio performance into AC-coupled loads. Patented design techniques achieve a clickless/popless power-up sequence, and the use of a low-current standby supply (SVCC) or external Schottky diode/reservoir capacitor combination allows clickless/popless power-down. A clickless/popless mute function is also provided to maintain a low impedance output when the input signal is switched off.
SVCC The MAX4298/MAX4299 provide a fully clickless powerdown sequence. SVCC can either be connected to a lowcurrent +5V power source or alternatively can be connected with a reservoir capacitor to ground and a Schottky diode to VCC. A reservoir capacitor of 220F or higher provides enough charge for the clickless powerdown sequence when CBIAS = 1F. For larger values of CBIAS, increase the reservoir capacitor accordingly. Short to VCC if clickless power-down is not needed. Driver Amplifier
The headphone driver amplifier is a class AB amplifier designed to drive 16 loads. The amplifiers have innovative architectures for both the input and output stages to achieve ultra-high PSRR while maintaining rail-to-rail output drive capability. The output stage can drive high capacitive loads encountered when driving long cables used for desktop speakers or headphones.
Mute Function
The MAX4298/MAX4299 have a MUTE pin that allows the user to mute the outputs of the device. This feature disconnects the input signal from the power amplifiers when a logic high is present at the MUTE pin. To ensure proper functionality, the MUTE pin should always be tied to either VCC or GND. MUTE only affects the headphone driver outputs. REG, BIAS, and MICOUT are unaffected. OUT1
8
Microphone Preamplifier (MAX4299)
The MAX4299 provides a microphone preamplifier that is a low-power version of the audio amplifier. It is intended to be used for low-level signal amplification. This microphone preamplifier provides rail-to-rail output with very high PSRR.
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Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator
Regulator (MAX4299)
The MAX4299 also has an additional 100mA lowdropout (LDO) regulator to provide clean analog power for other sensitive analog circuitry on the PC board, such as a typical PC99 audio codec or microphone biasing. It is designed to provide good AC line regulation. The nominal output voltage of REG is 3.3V, and is adjustable between 1.2V and 4.5V by connecting a resistor-divider from REG to GND. Connect FB to the junction of the resistor-divider. The input impedance at FB is typically 7k, which should be considered in output voltage calculations. REG should be bypassed to GND with at least 10F.
Layout
Good layout improves performance by decreasing the amount of stray capacitance and noise at the power amplifier's inputs and output. To decrease stray capacitance, minimize PC board trace lengths and resistor leads, and place external components as close to the pins as possible.
MAX4298/MAX4299
Power Dissipation
The first equation below indicates the maximum power dissipation point for a package that has two power amplifiers operating at identical known supply voltages and loads with sine wave inputs: PIC(DISS) = (VCC)2 / (2RL) [W] For example, with a 5V power supply and a load of 16, the maximum power dissipation of the amplifiers alone is 317mW. The additional power dissipation due to the 100mA regulator operating at maximum current is nominally 170mW, but will increase if the output is reduced externally from its nominal 3.3V. The regulator power consumption is given by: PREG = (VCC - VREG) x 100mA [W] To avoid thermal shutdown the sum of the regulator and amplifier power dissipation must not exceed the absolute maximum power-dissipation rating of the package.
Applications Information
Capacitor Selection and Regulator Stability
Normally, use a 10F capacitor on REG (MAX4299 only) and a 1F capacitor on CBYPASS. Larger capacitor values and lower ESRs provide better supply-noise rejection and line-transient response. Reduce noise and improve load-transient response, stability, and powersupply rejection by using larger capacitors. For stable operation over the full temperature range and load currents up to 100mA, a minimum of 10F (REG) and 1F (CBYPASS) is recommended. Use a 1F bypass capacitor on BIAS to ensure a fully clickless/popless power-up sequence. Smaller capacitor values may be used here to decrease the power-up time, but may cause the power-up transient to become audible. Larger bypass capacitors are not necessary to reduce noise and/or improve AC power-supply rejection. SVCC is the standby power supply. If using an external diode for charging, a 220F reservoir capacitor on SVCC provides standby power for the clickless powerdown sequence. Smaller capacitors here may cause an audible output transient on power-down; 220F or higher provides enough energy when CBIAS = 1F. For larger values of C BIAS, increase the reservoir capacitor accordingly.
Short-Circuit Protection and Thermal Shutdown
The MAX4298/MAX4299 have short-circuit current protection on all outputs. They also have a thermal shutdown function designed to protect the chip from junction temperatures in excess of +150C that may arise from temporary short circuits or operation beyond the power dissipation limit of the package. The driver amplifier outputs limit at around 220mA, the regulator at 150mA, and the microphone amplifier at +1.5mA/-12mA.
USB Applications
Universal serial bus (USB) interfaces are an increasingly popular method of interfacing medium-speed (up to 12Mbps) PC peripherals. One of the great benefits of the USB interface is the inclusion of a +5V supply. While this supply works well for a mouse or keyboard, its susceptibility for noise pickup can be unsuitable for highfidelity audio applications. The MAX4298/MAX4299s' excellent PSRR make them ideal candidates for USB applications due to their insensitivity to the supply noise. Of particular interest is an Internet-Protocol (IP) phone. This PC peripheral uses the local internet service provider as a free long-distance phone. The MAX4299, with its integral microphone amp, headphone driver, and linear regulator, can be a key element in the implementation of an IP phone that interfaces to the PC through the USB.
9
Mic Biasing (MAX4299)
Common microphone elements require resistive biasing to power their internal circuitry. A 2k resistor is typically used, and the microphone is AC-coupled to the microphone amplifier. If the microphone element allows low-voltage operation, biasing to the REG output provides excellent power-supply rejection.
Power Supply and Bypassing
The excellent PSRR of the MAX4298/MAX4299 allows them to operate from noisy power supplies. In most applications, a 0.1F capacitor from VCC to GND is sufficient. This bypass capacitor should be placed close to the VCC pin.
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Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator MAX4298/MAX4299
Typical Operating Circuits
RF 10k VCC OPTIONAL VCC
MAX4298
SVCC 220F RI 10k LEFT + _ 2.25V + _ OUT2 CAC 220F RF 10k IN1 BIAS 1F RI 10k OUT1 MUTE VCC CAC 220F RIGHT IN2 CBYPASS
GND
1F
20k VCC 10F REGON
AVDD
3.3V
REG FB
LDO
VCC SVCC
OPTIONAL
MAX4299
220F CAC 220F VCC
AUDIO CODEC
0.33F 20k 1F RIGHT 0.33F 20k MIC
BIAS
IN2
+ _
MICOUT CBYPASS 1F
200k
10
______________________________________________________________________________________
+ _ 2.25V + _ 20k
LEFT
IN1
OUT MUTE
OUT2 CAC 220F MICIN GND PGND
AVDD
RBIAS ELECTRET MIC
20k 0.33F
Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator
Pin Configurations (continued)
TOP VIEW
REG 1 FB 2 N.C. 3 OUT1 4 PGND 5 GND 6 IN1 7 BIAS 8 SVCC 9 MICOUT 10 20 REGON 19 N.C. 18 N.C. 17 VCC FB 1 OUT1 2 PGND 3 GND 4 IN1 5 BIAS 6 SVCC 7 MICOUT 8 16 REG 15 REGON 14 VCC N.C. 1 OUT1 GND 2 3 14 N.C. 13 VCC 12 OUT2
MAX4298/MAX4299
MAX4299
13 OUT2 12 IN2 11 CBYPASS 10 MUTE 9 MICIN
MAX4299
IN1 4 BIAS 5 SVCC 6 N.C. 7
MAX4298
11 IN2 10 CBYPASS 9 8 MUTE N.C.
16 OUT2 15 IN2 14 CBYPASS 13 MUTE 12 N.C. 11 MICIN
TSSOP
SO
WIDE SO
Chip Information
MAX4298 TRANSISTOR COUNT: 760 MAX4299 TRANSISTOR COUNT: 905 PROCESS: BiCMOS
Package Information
10LUMAX.EPS
______________________________________________________________________________________
11
Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator MAX4298/MAX4299
Package Information (continued)
SOICW.EPS
12
______________________________________________________________________________________
Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator MAX4298/MAX4299
Package Information (continued)
SOICN.EPS
______________________________________________________________________________________
13
Ultra-High PSRR Stereo Drivers + Microphone Amp + 100mA Linear Regulator MAX4298/MAX4299
Package Information (continued)
TSSOP,NO PADS.EPS
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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