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19-3781; Rev 2; 6/07
KIT ATION EVALU ABLE AVAIL
USB Peripheral Controller with SPI Interface
Features
Microprocessor-Independent USB Solution Complies with USB Specification Revision 2.0 (Full-Speed Operation) Integrated Full-Speed USB Transceiver Firmware/Hardware Control of an Internal D+ Pullup Resistor Programmable 3- or 4-Wire 26MHz SPI Interface Level Translators and VL Input Allow Independent System Interface Voltage Internal Comparator Detects VBUS for Self-Powered Applications ESD Protection on D+, D-, and VBCOMP Interrupt Output Pin (Level or Programmable Edge) Allows Polled or Interrupt-Driven SPI Interface Intelligent USB Serial-Interface Engine (SIE) Automatically Handles USB Flow Control and Double Buffering Handles Low-Level USB Signaling Details Contains Timers for USB Time-Sensitive Operations So SPI Master Does Not Need to Time Events Built-In Endpoint FIFOs EP0: CONTROL (64 Bytes) EP1: OUT, Bulk or Interrupt, 2 x 64 Bytes (Double-Buffered) EP2: IN, Bulk or Interrupt, 2 x 64 Bytes (Double-Buffered) EP3: IN, Bulk or Interrupt (64 Bytes) Double-Buffered Data Endpoints Increase Throughput by Allowing the SPI Master to Transfer Data Concurrently with USB Transfers Over the Same Endpoint SETUP Data Has Its Own 8-Byte FIFO, Simplifying Firmware Four General-Purpose Inputs and Four GeneralPurpose Outputs Space-Saving LQFP and TQFN Packages
C32-1
General Description
The MAX3420E contains the digital logic and analog circuitry necessary to implement a full-speed USB peripheral compliant to USB specification rev 2.0. A built-in full-speed transceiver features 15kV ESD protection and programmable USB connect and disconnect. An internal serial-interface engine (SIE) handles low-level USB protocol details such as error checking and bus retries. The MAX3420E operates using a register set accessed by an SPITM interface that operates up to 26MHz. Any SPI master (microprocessor, ASIC, DSP, etc.) can add USB functionality using the simple 3- or 4-wire SPI interface. Internal level translators allow the SPI interface to run at a system voltage between 1.71V and 3.6V. USB timed operations are done inside the MAX3420E with interrupts provided at completion so an SPI master does not need timers to meet USB timing requirements. The MAX3420E includes four general-purpose inputs and outputs so any microprocessor that uses I/O pins to implement the SPI interface can reclaim the I/O pins and gain additional ones. The MAX3420E operates over the extended -40C to +85C temperature range and is available in a 32-pin LQFP package (7mm x 7mm) and a space-saving 24pin TQFN package (4mm x 4mm).
MAX3420E
Applications
Cell Phones PC Peripherals Microprocessors and DSPs Custom USB Devices Cameras Desktop Routers PLCs Set-Top Boxes PDAs MP3 Players Instrumentation
Ordering Information
PART TEMP RANGE PINPACKAGE 24 TQFN-EP* 4mm x 4mm x 0.8mm 32 LQFP 7mm x 7mm x 1.4mm PACKAGE CODE T2444-4
MAX3420EETG+ -40C to +85C
MAX3420EECJ+ -40C to +85C
SPI is a trademark of Motorola, Inc.
+Denotes lead-free package. *EP = Exposed paddle, connected to ground. ________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
USB Peripheral Controller with SPI Interface MAX3420E
Typical Application Circuits
3.3V REGULATOR SPI 3, 4 USB
MAX3420E
INT
P
The MAX3420E connects to any microprocessor using 3 or 4 interface pins (Figure 1). On a simple microprocessor without SPI hardware, these can be bitbanged general-purpose I/O pins. Four GPIN and four GPOUT pins on the MAX3420E more than replace the P pins necessary to implement the interface. Although the MAX3420E SPI hardware includes separate data-in (MOSI, (master-out, slave-in)) and data-out (MISO, (master-in, slave-out)) pins, the SPI interface can also be configured for the MOSI pin to carry bidirectional data, saving an interface pin. This is referred to as halfduplex mode.
Figure 1. The MAX3420E Connects to Any Microprocessor Using 3 or 4 Interface Pins
3.3V REGULATOR SPI 3, 4
POWER RAIL
USB
Two MAX3420E features make it easy to connect to large, fast chips such as ASICs and DSPs (see Figure 2). First, the SPI interface can be clocked up to 26MHz. Second, a VL pin and internal level translators allow running the system interface at a lower voltage than the 3.3V required for VCC.
MAX3420E
INT ASIC, DSP, ETC.
Figure 2. The MAX3420E Connected to a Large Chip
3.3V REGULATOR
LOCAL POWER
USB
MAX3420E
I S O L A T O R S
MISO INT MICRO ASIC DSP SCLK MOSI SS LOCAL GND
The MAX3420E provides an ideal method for electrically isolating a USB interface (Figure 3). USB employs flow control in which the MAX3420E automatically answers host requests with a NAK handshake, until the microprocessor completes its data-transfer operations over the SPI port. This means that the SPI interface can run at any frequency up to 26MHz. Therefore, the designer is free to choose the interface operating frequency and to make opto-isolator choices optimized for cost or performance.
Figure 3. Optical Isolation of USB Using the MAX3420E
2
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USB Peripheral Controller with SPI Interface
Functional Diagram
VL RES XI XO
MAX3420E
VCC INTERNAL POR
RESET LOGIC 1.5k
OSC AND PLL 4x
POWER DOWN D+ DESD PROTECTION FULL-SPEED USB TRANSCEIVER USB SIE (SERIAL-INTERFACE ENGINE)
48MHz
SCLK
MOSI SPI SLAVE INTERFACE ENDPOINT BUFFERS SS VBCOMP ESD PROTECTION VBUS COMP 1V TO 3V RGPIN VBUS_DET
MISO
INT
OPERATE
VBUS_DET BUSACT 1 MUX 2
SOF 3
MAX3420E
0
GND GPX GPIN3 GPIN2 GPIN1 GPIN0 GPOUT3 GPOUT1 GPOUT0
GPOUT2
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USB Peripheral Controller with SPI Interface MAX3420E
Pin Description
PIN TQFN 1 2 LQFP 1 2 NAME GPOUT0 Output GPOUT1 INPUT/ OUTPUT FUNCTION General-Purpose Push-Pull Outputs. GPOUT3-GPOUT0 logic levels are referenced to the voltage on VL. The SPI master controls the GPOUT3-GPOUT0 states by writing to bit 3 through bit 0 of the IOPINS (R20) register. Level-Translator Reference Voltage. Connect VL to the system's 1.71V to 3.6V logic-level power supply. Bypass VL to ground with a 0.1F capacitor as close to the VL pin as possible. Ground General-Purpose Push-Pull Outputs. GPOUT3-GPOUT0 logic levels are referenced to the voltage on VL. The SPI master controls the GPOUT3-GPOUT0 states by writing to bit 3 through bit 0 of the IOPINS (R20) register. Device Reset. Drive RES low to clear all of the internal registers except for PINCTL (R17), USBCTL (R15), and SPI logic. See the Device Reset section for a description of resets available on the MAX3420E. Note: The MAX3420E is internally reset if either VCC of VL is not present. The register file is not accessible under these conditions. SPI Serial-Clock Input. An external SPI master supplies this clock with frequencies up to 26MHz. The logic level is referenced to the voltage on VL. Data is clocked into the SPI slave interface on the positive edge of SCLK. Data is clocked out of the SPI slave interface on the falling edge of SCLK. SPI Slave-Select Input. The SS logic level is referenced to the voltage on VL. When SS is driven high, the SPI slave interface is not selected and SCLK transitions are ignored. An SPI transfer begins with a high-to-low SS transition and ends with a low-to-high SS transition. SPI Serial-Data Output (Master-In, Slave-Out). MISO is a push-pull output. MISO is tri-stated in half-duplex mode or when SS = 1. The MISO logic level is referenced to the voltage on VL. SPI Serial-Data Input (Master-Out, Slave-In). The logic level on MOSI is referenced to the voltage on VL. MOSI can also be configured as a bidirectional MOSI/MISO input and output. General-Purpose Multiplexed Output. The internal MAX3420E signal that appears on GPX is programmable by writing to the GPXB and GPXA bits of the PINCTL (R17) register. GPX indicates one of four signals: OPERATE (00, default), VBUS_DET (01), BUSACT (10), and SOF (11). Interrupt Output. In edge mode, the logic level on INT is referenced to the voltage on VL. In edge mode, INT is a push-pull output with programmable polarity. In level mode, INT is open-drain and active low. Set the IE bit in the CPUCTL (R16) register to enable INT. USB D- Signal. Connect D- to a USB "B" connector through a 33 1% series resistor.
3
3, 4
VL GND GPOUT2
Input
4, 14 5 6
5, 6, 18, 19 7 8
Input Output
GPOUT3
7
10
RES
Input
8
11
SCLK
Input
9
12
SS
Input
10
13
MISO
Output Input or Input/ Output
11
14
MOSI
12
15
GPX
Output
13
17
INT
Output
15
20
D-
Input/ Output
4
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USB Peripheral Controller with SPI Interface
Pin Description (continued)
PIN TQFN 16 LQFP 21 NAME D+ INPUT/ OUTPUT Input/ Output Input FUNCTION USB D+ Signal. Connect D+ to a USB "B" connector through a 33 1% series resistor. The 1.5k D+ pullup resistor is internal to the device. USB Transceiver Power-Supply Input. Connect VCC to a positive 3.3V power supply. Bypass VCC to ground with a 1.0F ceramic capacitor as close to the VCC pin as possible. VBUS Comparator Input. VBCOMP is internally connected to a voltage comparator to allow the SPI master to detect (through an interrupt or checking a register bit) the presence or loss of power on VBUS. Bypass VBCOMP to ground with a 1.0F ceramic capacitor. Crystal Oscillator Input. Connect XI to one side of a parallel resonant 12MHz 0.25% crystal and a capacitor to GND. XI can also be driven by an external clock referenced to VCC. Crystal Oscillator Output. Connect XO to the other side of a parallel resonant 12MHz 0.25% crystal and a capacitor to GND. Leave XO unconnected if XI is driven with an external source. General-Purpose Inputs. GPIN3-GPIN0 are connected to VL with internal pullup resistors. GPIN3-GPIN0 logic levels are referenced to the voltage on VL. The SPI master samples GPIN3-GPIN0 states by reading bit 7 through bit 4 of the IOPINS (R20) register. Writing to these bits has no effect. No Internal Connection Exposed Paddle on the Bottom of the TQFN Package. Connect EP to GND.
MAX3420E
17
22, 23
VCC
18
24
VBCOMP
Input
19
26
XI
Input
20 21 22 23 24 -- EP
27 29 30 31 32 9, 16, 25, 28 --
XO GPIN0 GPIN1 GPIN2 GPIN3 N.C. GND
Output
Input
-- Input
Register Description
The SPI master controls the MAX3420E by reading and writing 21 registers (Table 1). For a complete description of register contents, please refer to the "MAX3420E Programming Guide." A register access consists of the SPI master first writing an SPI command byte, followed by reading or writing the contents of the addressed register. All SPI transfers are MSB first. The command byte contains the register address, a direction bit (read = 0, write = 1), and the ACKSTAT bit (Figure 4). The SPI master addresses the MAX3420E registers by writing the binary value of the register number in the Reg4 through Reg0 bits of the command byte. For example, to access the IOPINS (R20) register, the Reg4 through
b7 Reg4 b6 Reg3 b5 Reg2 b4 Reg1
Reg0 bits would be as follows: Reg4 = 1, Reg3 = 0, Reg2 = 1, Reg1 = 0, Reg0 = 0. The DIR (direction) bit determines the direction for the data transfer. DIR = 1 means the data byte(s) will be written to the register, and DIR = 0 means the data byte(s) will be read from the register. The ACKSTAT bit sets the ACKSTAT bit in the EPSTALLS (R9) register. The SPI master sets this bit to indicate that it has finished servicing a CONTROL transfer. Since the bit is frequently used, having it in the SPI command byte improves firmware efficiency. In SPI full-duplex mode, the MAX3420E clocks out eight USB status bits as the command byte is clocked in (Figure 5). In half-duplex mode, these status bits are accessed in the normal way, as register bits.
b3 Reg0 b2 0 b1 DIR b0 ACKSTAT
Figure 4. SPI Command Byte
b7 SUSPIRQ b6 URESIRQ b5 SUDAVIRQ b4 IN3BAVIRQ b3 IN2BAVIRQ b2 OUT1DAVIRQ b1 OUT0DAVIRQ b0 IN0BAVIRQ
Figure 5. USB Status Bits Clocked Out as First Byte of Every Transfer (Full-Duplex Mode Only) _______________________________________________________________________________________ 5
USB Peripheral Controller with SPI Interface MAX3420E
The first five registers (R0-R4) access endpoint FIFOs. To access a FIFO, an initial command byte sets the register address and then consecutive reads or writes keep the same register address to access subsequent FIFO bytes. The remaining registers (R5-R20) control the operation of the MAX3420E. Once a register address above R4 is set in the command byte, successive byte reads or writes in the same SPI access cycle (SS low) increment the register address after every byte read or written. This incrementing operation continues until R20 is accessed. Subsequent byte reads or writes continue to access R20. Note that this autoincrementing action stops with the next SPI cycle, which establishes a new register address. Addressing beyond R20 is ignored. The MAX3420E register map is depicted in Table 1. For a complete description of all register contents, please refer to the MAX3420E Programming Guide.
Table 1. MAX3420E Register Map
REG R0 R1 R2 R3 R4 R5 R6 R7 R8 R9 NAME EP0FIFO EP1OUTFIFO EP2INFIFO EP3INFIFO SUDFIFO EP0BC EP1OUTBC EP2INBC EP3INBC EPSTALLS b7 b7 b7 b7 b7 b7 0 0 0 0 0 EP3DISAB 0 0 b6 b6 b6 b6 b6 b6 b6 b6 b6 b6 ACKSTAT EP2DISAB 0 0 b5 b5 b5 b5 b5 b5 b5 b5 b5 b5 STLSTAT EP1DISAB b4 b4 b4 b4 b4 b4 b4 b4 b4 b4 STLEP3IN CTGEP3IN b3 b3 b3 b3 b3 b3 b3 b3 b3 b3 STLEP2IN b2 b2 b2 b2 b2 b2 b2 b2 b2 b2 STLEP1OUT b1 b1 b1 b1 b1 b1 b1 b1 b1 b1 STLEP0OUT 0 b0 b0 b0 b0 b0 b0 b0 b0 b0 b0 acc RSC RSC RSC RSC RSC RSC RSC RSC RSC
STLEP0IN RSC 0 RSC
R10 CLRTOGS R11 EPIRQ R12 EPIEN R13 USBIRQ R14 USBIEN R15 USBCTL R16 CPUCTL R17 PINCTL R18 REVISION R19 FNADDR R20 IOPINS
CTGEP2IN CTGEP1OUT
SUDAVIRQ IN3BAVIRQ IN2BAVIRQ OUT1DAVIRQ OUT0DAVIRQ IN0BAVIRQ RC SUDAVIE IN3BAVIE SUSPIRQ SUSPIE IN2BAVIE URESIRQ URESIE OUT1DAVIE BUSACTIRQ BUSACTIE SIGRWU 0 POSINT 1 b2 GPOUT2 OUT0DAVIE IN0BAVIE RSC
URESDNIRQ VBUSIRQ NOVBUSIRQ URESDNIE HOSCSTEN 0 EP3INAK 0 0 GPIN3 VBUSIE VBGATE 0 EP2INAK 0 b6 GPIN2 NOVBUSIE CHIPRES 0 EP0INAK 0 b5 GPIN1
RWUDNIRQ OSCOKIRQ RC RWUDNIE 0 0 GPXB 0 b1 GPOUT1 OSCOKIE RSC 0 IE GPXA 0 b0 GPOUT0 RSC RSC RSC R R RSC
PWRDOWN CONNECT 0 FDUPSPI 0 b4 GPIN0 0 INTLEVEL 0 b3 GPOUT3
Note: The acc (access) column indicates how the SPI master can access the register. R = read, RC = read or clear, RSC = read, set, or clear. Writing to an R register (read only) has no effect. Writing a 1 to an RC bit (read or clear) clears the bit. Writing a zero to an RC bit has no effect.
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USB Peripheral Controller with SPI Interface
Pin Configurations
VBCOMP
MAX3420E
TOP VIEW
VBCOMP
TOP VIEW
GND
GND 18
VCC
VCC
D+
GND
VCC
18 XI 19 XO 20 GPIN0 21 GPIN1 22 GPIN2 23 GPIN3 24 + 1 GPOUT0
17
16
15
14
INT
D+
D-
24 N.C. 12 GPX 11 MOSI 10 MISO XI XO N.C. GPIN0 GPIN1 GPIN2 GPIN3 25 26 27 28 29 30 31 32 + 1 GPOUT0
23
22
21
20
19
17 16 15 14 13 N.C. GPX MOSI MISO SS SCLK RES N.C.
13
MAX3420E
*EP
9 8 7
SS SCLK RES
MAX3420E
INT 12 11 10 9 8 GPOUT3
2 GPOUT1
3 VL
4 GND
5 GPOUT2
6 GPOUT3
D5 GND
2 GPOUT1
3 VL
4 VL
6 GND
7 GPOUT2
TQFN
* EXPOSED PADDLE CONNECTED TO GROUND
LQFP
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USB Peripheral Controller with SPI Interface MAX3420E
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted.) VCC ......................................................................... -0.3V to +4V VL .............................................................................-0.3V to +4V VBCOMP .................................................................-0.3V to +6V D+, D-, XI, XO ............................................-0.3V to (VCC + 0.3V) SCLK, MOSI, MISO, SS, RES, GPOUT3-GPOUT0, GPIN3-GPIN0, GPX, INT ..........................-0.3V to (VL + 0.3V) Continuous Power Dissipation (TA = +70C) 24-Pin TQFN (derate 20.8mW/C above +70C) .......1667mW 32-Pin LQFP (derate 20.7mW/C above +70C)........1653mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C 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 = +3V to +3.6V, VL = +1.71V to +3.6V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.3V, VL = +2.5V, TA = +25C.) (Note 1)
PARAMETER DC CHARACTERISTICS Supply Voltage VCC Logic-Core Supply and LogicInterface Voltage VL VCC Supply Current VCC VL Continuously transmitting on D+ and D- at 12Mbps, CL = 50pF on D+ and D- to GND, CONNECT = 0 SCLK toggling at 20MHz, SS = low, GPIN3-GPIN0 = 0 D+ = high, D- = low CONNECT = 0, PWRDOWN = 1 CONNECT = 0, PWRDOWN = 1 ILOAD = +5mA, VL < 2.5V ILOAD = +10mA, VL 2.5V ILOAD = -20mA, VL < 2.5V ILOAD = -20mA, VL 2.5V 2/3 x VL 0.4 1 10 20 30 VL - 0.45 VL - 0.4 0.6 0.4 3.0 1.71 3.3 3.6 3.60 V V SYMBOL CONDITIONS MIN TYP MAX UNITS
ICC
15
30
mA
VL Supply Current VCC Supply Current During Idle VCC Suspend Supply Current VL Suspend Supply Current LOGIC-SIDE I/O MISO, GPOUT3-GPOUT0, GPX, INT Output High Voltage MISO, GPOUT3-GPOUT0, GPX, INT Output Low Voltage SCLK, MOSI, GPIN3-GPIN0, SS, RES Input High Voltage SCLK, MOSI, GPIN3-GPIN0, SS, RES Input Low Voltage SCLK, MOSI, SS, RES Input Leakage Current GPIN3-GPIN0 Pullup Resistor to VL TRANSCEIVER SPECIFICATIONS Differential-Receiver Input Sensitivity Differential-Receiver CommonMode Voltage
IL ICCID ICCSUS ILSUS
6 1.5 33 15
20 5 100 50
mA mA A A
VOH VOL VIH VIL IIL RGPIN
V V V V A k
|VD+ - VD-|
0.2 0.8 2.5
V V
8
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USB Peripheral Controller with SPI Interface
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +3V to +3.6V, VL = +1.71V to +3.6V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.3V, VL = +2.5V, TA = +25C.) (Note 1)
PARAMETER Single-Ended Receiver Input Low Voltage Single-Ended Receiver Input High Voltage Single-Ended Receiver Hysteresis Voltage D+, D- Input Impedance D+, D- Output Low Voltage D+, D- Output High Voltage Driver Output Impedance Excluding External Resistor D+ Pullup Resistor ESD PROTECTION (D+, D-, VBCOMP) Human Body Model IEC61000-4-2 Air-Gap Discharge IEC61000-4-2 Contact Discharge THERMAL SHUTDOWN Thermal-Shutdown Low-to-High Thermal-Shutdown High-to-Low CRYSTAL OSCILLATOR SPECIFICATIONS (XI, XO) XI Input High Voltage XI Input Low Voltage XI Input Current XI, XO Input Capacitance VBCOMP COMPARATOR SPECIFICATIONS VBCOMP Comparator Threshold VBCOMP Comparator Hysteresis VBCOMP Comparator Input Impedance VTH VHYS RIN 100 1.0 2.0 375 3.0 V mV k 3 2/3 x VCC VCC 0.4 10 V V A pF +160 +140 C C 1F ceramic capacitors from VBCOMP and VCC to GND 1F ceramic capacitors from VBCOMP and VCC to GND 1F ceramic capacitors from VBCOMP and VCC to GND 15 12 8 kV kV kV VOL VOH RL = 1.5k from D+ to 3.6V RL = 15k from D+ and D- to GND (Note 2) REXT = 33 2.8 2 1.425 7 1.5 300 0.3 3.6 11 1.575 SYMBOL VIL VIH 2.0 0.2 CONDITIONS MIN TYP MAX 0.8 UNITS V V V k V V k
MAX3420E
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USB Peripheral Controller with SPI Interface MAX3420E
TIMING CHARACTERISTICS
(VCC = +3V to +3.6V, VL = +1.71V to +3.6V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +3.3V, VL = +2.5V, TA = +25C.) (Note 1)
PARAMETER D+, D- Rise Time D+, D- Fall Time Rise-/Fall-Time Matching Output-Signal Crossover Voltage
SYMBOL tRISE tFALL
CONDITIONS CL = 50pF, Figures 6 and 7 CL = 50pF, Figures 6 and 7 CL = 50pF, Figures 6 and 7 (Note 2) CL = 50pF, Figures 6 and 7 (Note 2) VL = 1.71V VL = 2.5V
MIN 4 4 90 1.3 77.0 38.4 17 17 20 30 30 5 10 200 14.2 14.2 3.5
TYP
MAX 20 20 110 2.0
UNITS ns ns % V
USB TRANSMITTER TIMING CHARACTERISTICS
SPI BUS TIMING CHARACTERISTICS (VL = 2.5V) (Figures 8 and 9) (Note 3) Serial Clock (SCLK) Period (Note 4) SCLK Pulse-Width High SCLK Pulse-Width Low SS Fall to MISO Valid SS Leading Time Before the First SCLK Edge SS Trailing Time After the Last SCLK Edge Data-In Setup Time Data-In Hold Time SS Pulse High SCLK Fall to MISO Propagation Delay SCLK Fall to MOSI Propagation Delay SCLK Fall to MOSI Drive SS High to MOSI High Impedance Time-to-Enter Suspend Time-to-Exit Suspend tCP tCH tCL tCSS tL tT tDS tDH tCSW tDO tDI tON tOFF ns ns ns ns ns ns ns ns ns ns ns ns 20 ns
SUSPEND TIMING CHARACTERISTICS PWRDOWN = 1 to oscillator stop PWRDOWN = 1 to 0 to OSCOKIRQ (Note 5) 3 5 s ms
Note 1: Note 2: Note 3: Note 4: Note 5:
Parameters are 100% production tested at TA = +25C, and guaranteed by correlation over temperature. Design guaranteed by bench testing. Limits are not production tested. At VL = 1.71V to 2.5V, derate all of the SPI timing characteristics by 50%. Not production tested. The minimum period is derived from SPI timing parameters. Time-to-exit suspend is dependent on the crystal used.
10
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USB Peripheral Controller with SPI Interface MAX3420E
Test Circuits and Timing Diagrams
tRISE tFALL TEST POINT
MAX3420E
VOH D+ OR D90%
33
CL VOL 10%
15k
Figure 6. Rise and Fall Times
tL SS tCSS
Figure 7. Load for D+/D- AC Measurements
tCSW tCL tCH tT
1 SCLK tDS
2
8
9 tCP
10
16
MOSI
tDH HIGH IMPEDANCE
tDO HIGH IMPEDANCE
MISO
Figure 8. SPI Bus Timing Diagram (Full-Duplex Mode, SPI Mode (0,0))
tL SS tCSW
tCL
tCH
tT
1 SCLK tDS MOSI
2
8
9 tCP
10
16
HI-Z
tDH HIGH IMPEDANCE
tON
tDI
tOFF HIGH IMPEDANCE
MISO
NOTES: 1) DURING THE FIRST 8 CLOCKS CYCLES, THE MOSI PIN IS HIGH IMPEDANCE AND THE SPI MASTER DRIVES DATA ONTO THE MOSI PIN. SETUP AND HOLD TIMES ARE THE SAME AS FOR FULL-DUPLEX MODE. 2) FOR SPI WRITE CYCLES, THE MOSI PIN CONTINUES TO BE HIGH IMPEDANCE AND THE EXTERNAL MASTER CONTINUES TO DRIVE MOSI. 3) FOR SPI READ CYCLES, AFTER THE 8TH CLOCK-RISING EDGE, THE MAX3420E STARTS DRIVING THE MOSI PIN AFTER TIME tON. THE EXTERNAL MASTER MUST TURN OFF ITS DRIVER TO THE MOSI PIN BEFORE tON TO AVOID CONTENTION. PROPAGATION DELAYS ARE THE SAME AS FOR THE MOSI PIN IN FULL-DUPLEX MODE.
Figure 9. SPI Bus Timing Diagram (Half-Duplex Mode, SPI Mode (0,0)) ______________________________________________________________________________________ 11
USB Peripheral Controller with SPI Interface MAX3420E
Typical Operating Characteristics
(VCC = +3.3V, VL = +3.3V, TA = +25C.)
EYE DIAGRAM
4
MAX3420E toc01
3 D+ AND D- (V) 2 1 0 -1 0 10 20 30 40 50 60 70 80 TIME (ns)
Detailed Description
The MAX3420E contains the digital logic and analog circuitry necessary to implement a full-speed USB peripheral that complies with the USB specification rev 2.0. ESD protection of 15kV is provided on D+, D-, and VBCOMP. The MAX3420E features an internal USB transceiver and an internal 1.5k resistor that connects between D+ and VCC under the control of a register bit (CONNECT). This allows a USB peripheral to control the logical connection to the USB host. Any SPI master can communicate with the MAX3420E through the SPI slave interface that operates in SPI mode (0,0) or (1,1). An SPI master accesses the MAX3420E by reading and writing to internal registers. A typical data transfer consists of writing a first byte that sets a register address and direction with additional bytes reading or writing data to the register or internal FIFO. The MAX3420E contains 384 bytes of endpoint buffer memory, implementing the following endpoints: * EP0: 64-byte bidirectional CONTROL endpoint * EP1: 2 x 64-byte double-buffered BULK/INT OUT endpoint * EP2: 2 x 64-byte double-buffered BULK/INT IN endpoint * EP3: 64-byte BULK/INT IN endpoint The choice to use EP1, EP2, EP3 as BULK or INTERRUPT endpoints is strictly a function of the endpoint descriptors that the SPI master returns to the USB host during enumeration.
12
The MAX3420E register set and SPI interface is optimized to reduce SPI traffic. An interrupt output pin, INT, notifies the SPI master when USB service is required: when a packet arrives, a packet is sent, or the host suspends or resumes bus activity. Double-buffered endpoints help sustain bandwidth by allowing data to move concurrently over USB and the SPI interface.
VCC
Power the USB transceiver by applying a positive 3.3V supply to V CC . Bypass V CC to GND with a 1.0F ceramic capacitor as close to the VCC pin as possible.
VL
The MAX3420E digital core is powered though the VL pin. VL also acts as a reference level for the SPI interface and all other inputs and outputs. Connect VL to the system's logic-level power supply. Internal level translators and VL allow the SPI interface and all general-purpose inputs and outputs to operate at a system voltage between 1.71V and 3.6V.
VBCOMP
The MAX3420E features a USB VBUS detector input, VBCOMP. The VBCOMP pin can withstand input voltages up to 6V. Bypass VBCOMP to GND with a 1.0F ceramic capacitor. According to USB specification rev 2.0, a self-powered USB device must not power the 1.5k pullup resistor on D+ if the USB host turns off VBUS. VBCOMP is internally connected to a voltage comparator so that the SPI master can detect the loss of VBUS (through an interrupt (INT) or checking a bit
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USB Peripheral Controller with SPI Interface MAX3420E
Table 2. Internal Pullup Resistor Control
CONNECT 0 1 1 1 VBGATE X 0 1 1 VBUS_DET X X 0 1 PULLUP Not Connected Connected Not Connected Connected
INTLEVEL = 1 POSINT = X INTLEVEL = 0 POSINT = 0 INTLEVEL = 0 POSINT = 1 (1) INT INT (2) INT SINGLE IRQ CLEAR IRQ FIRST IRQ ACTIVE SECOND IRQ ACTIVE CLEAR FIRST IRQ, SECOND , IRQ STILL ACTIVE CLEAR LAST PENDING IRQ
(NOVBUSIRQ)) and disconnect the internal 1.5k pullup resistor. If the device using the MAX3420E is bus powered (through a +3.3V regulator connected to VCC), the MAX3420E VBCOMP input can be used as a general-purpose input. Using VBCOMP as a generalpurpose input requires a 10k pullup resistor from VBCOMP to VL. See the Applications Information section for more details about this connection.
(1) WIDTH DETERMINED BY TIME TAKEN TO CLEAR THE IRQ (2) 10.67s
Figure 10. Behavior of the INT Pin for Different INTLEVEL and POSINT Bit Settings
D+ and DThe internal USB full-speed transceiver is brought out to the bidirectional data pins D+ and D-. These pins are 15kV ESD protected. Connect D+ and D- to a USB "B" connector through 33 1% series resistors. A switchable 1.5k pullup resistor is internally connected to D+. According to the USB rev 2.0 specification, a self-powered peripheral must disconnect its 1.5k pullup resistor to D+ in the event that the host turns off bus power. The VBGATE bit in the USBCTL (R15) register provides the option for the MAX3420E internal logic to automatically disconnect the 1.5k resistor on D+. The VBGATE and CONNECT bits of USBCTL (R15), along with the VBCOMP comparator output (VBUS_DET), control the pullup resistor between VCC and D+, as shown in Table 2. Note that if VBGATE = 1 and VBUS_DET = 0, the pullup resistor is disconnected regardless of the CONNECT bit setting.
RES
Drive RES low to put the MAX3420E into a chip reset. A chip reset sets all registers to their default states, except for PINCTL (R17), USBCTL (R15), and SPI logic. All FIFO contents are unknown during chip reset. Bring the MAX3420E out of chip reset by driving RES high. The RES pulse width can be as short as 200ns. See the Device Reset section for a description of the resets available on the MAX3420E.
INT
The MAX3420E INT output pin signals when a USB event occurs that requires the attention of the SPI master. The SPI master must set the IE bit in the CPUCTL (R16) register to activate INT. When the IE bit is cleared, INT is inactive (open for level mode, high for negative edge, low for positive edge). INT is inactive upon power-up or after a chip reset. The INT pin can be a push-pull or open-drain output. Set the INTLEVEL bit of the PINCTL (R17) register high to program the INT output pin to be an active-low level (open-drain output). An external pullup resistor to VL is required for this setting. In level mode, the MAX3420E drives INT low when any of the interrupt flags are set. If multiple interrupts are pending, INT goes inactive only when the SPI master clears the last active interrupt request bit (Figure 10). The POSINT bit of the PINCTL (R17) register has no effect on INT in level mode. Clear the INTLEVEL bit to program INT to be an edge (push-pull output). The active edge is programmable using the POSINT bit of the PINCTL (R17) register. In edge mode, the MAX3420E produces an edge referenced to VL any time an interrupt request is activated, or when an interrupt request is cleared and others are
13
XI and XO
XI and XO connect an external 12MHz crystal to the internal oscillator circuit. XI is the crystal oscillator input, and XO is the crystal oscillator output. Connect one side of an external 12MHz 0.25% parallel resonant crystal to XI, and connect XO to the other side. Connect load capacitors (20pF max) to ground on both XI and XO. XI can also be driven with an external 12MHz 0.25% clock. If driving XI with an external clock, leave XO unconnected. The external clock must meet the voltage characteristics depicted in the Electrical Characteristics table. Internal logic is singleedge triggered. The external clock should have a nominal 50% duty cycle.
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USB Peripheral Controller with SPI Interface MAX3420E
pending (Figure 10). Set the POSINT bit in the PINCTL (R17) register to make INT active high, and clear the POSINT bit to make INT active low.
GPOUT WRITE REGISTER BIT GPOUT PIN
GPIN3-GPIN0, GPOUT3-GPOUT0 and GPX
The MAX3420E has four general-purpose inputs (GPIN3-GPIN0), four general-purpose outputs (GPOUT3-GPOUT0), and a multiplexed output pin (GPX). GPIN3 through GPIN0 all have weak internal pullup resistors to VL. These inputs can be read by sampling bits 7 through 4 of the IOPINS (R20) register. Writing to GPIN3 through GPIN0 has no effect. GPOUT3 through GPOUT0 are the general-purpose outputs. Update these outputs by writing to bits 3 through 0 of the IOPINS (R20) register. GPOUT3- GPOUT0 logic levels are referenced to the voltage on V L . As shown in Figure 11, reading the state of a GPOUT3-GPOUT0 bit returns the state of the internal register bit, not the actual pin state. This is useful for doing read-modify-write operations to an output pin (such as blinking an LED), since the load on the output pin does not affect the register logic state. GPX is a push-pull output with a 4-way multiplexer that selects its output signal. The logic level on GPX is referenced to VL. The SPI master writes to the GPXB and
GPOUT READ
Figure 11. Behavior of Read and Write Operations on GPOUT3-GPOUT0
FULL-SPEED TIME FRAME 1ms USB PACKETS GPX SOF SOF FULL-SPEED TIME FRAME 1ms SOF
~50%
Figure 12. GPX Output in SOF Mode
MOSI
Table 3. GPX Output State
GPXB 0 0 1 1 GPXA 0 1 0 1 GPX PIN OUTPUT OPERATE (Default State) VBUS_DET BUSACT SOF
FDUPSPI = 1
MISO
MAX3420E
MOSI FDUPSPI = 0 (DEFAULT)
GPXA bits of PINCTL (R17) register to select one of four internal signals as depicted in Table 3. * OPERATE: This signal goes high when the MAX3420E is able to operate after a power-up or RES reset. OPERATE is the default GPX output. * VBUS_DET: VBUS_DET is the VBCOMP comparator output. This allows the user to directly monitor the VBUS status. * BUSACT: USB BUS activity signal (active-high). This signal is active whenever there is traffic on the USB bus. The BUSACT signal is set whenever a SYNC field is detected. BUSACT goes low during bus reset or after 32-bit times of J-state. * SOF: A square wave with a positive edge that indicates the USB start-of-frame (Figure 12).
MISO
MAX3420E
Figure 13. MAX3420E SPI Data Pins for Full-Duplex (Top) and Half-Duplex (Bottom) Operation
MOSI (Master-Out, Slave-In) and MISO (Master-In, Slave-Out)
The SPI data pins MOSI and MISO operate differently depending on the setting of a register bit called FDUPSPI (full-duplex SPI). Figure 13 shows the two configurations according to the FDUPSPI bit setting.
14
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USB Peripheral Controller with SPI Interface MAX3420E
SS SPI MODE 0,0 OR 1,1
MISO
Q7
Q6
Q5
Q4
Q3
Q2
Q1
Q0
*
SCLK MODE 0,0 SCLK MODE 1,1
MOSI
D7
D6
D5
D4
D3
D2
D1
D0
*
*MSB OF NEXT BYTE IN BURST MODE (SS REMAINS LOW)
Figure 14. SPI Clocking Modes
In full-duplex mode (FDUPSPI = 1), the MOSI and MISO pins are separate, and the MISO pin drives only when SS is low. In this mode, the first eight SCLK edges (after SS = 0) clock the command byte into the MAX3420E on MOSI, and eight USB status bits are clocked out of the MAX3420E on MISO. For an SPI write cycle, any bytes following the command byte are clocked into the MAX3420E on MOSI, and zeros are clocked out on MISO. For an SPI read cycle, any bytes following the command byte are clocked out of the MAX3420E on MISO and the data on MOSI is ignored. At the conclusion of the SPI cycle (SS = 1), the MISO output tri-states. In half-duplex mode, the MOSI pin is a bidirectional pin and the MISO pin is tri-stated. This saves a pin in the SPI interface. Because of the shared data pin, this mode does not offer the eight USB status bits (Figure 5) as the command byte is clocked into the MAX3420E. The MISO pin can be left unconnected in half-duplex mode.
If SS goes high before a complete byte is clocked in, the byte-in-progress is discarded. The SPI master can terminate an SPI cycle after clocking in the first 8 bits (the command byte). This feature can be used in a fullduplex system to retrieve the USB status bits (Figure 5) without sending or receiving SPI data.
Applications Information
SPI Interface
The MAX3420E operates as an SPI slave device. A register access consists of the SPI master first writing an SPI command byte, followed by reading or writing the contents of the addressed register (see the Register Description section for more details). All SPI transfers are MSB first. The external SPI master provides a clock signal to the MAX3420E SCLK input. This clock frequency can be between DC and 26MHz. Bit transfers occur on the positive edge of SCLK. The MAX3420E counts bits and divides them into bytes. If fewer than 8 bits are clocked into the MAX3420E when SS goes high, the MAX3420E discards the partial byte. The MAX3420E SPI interface operates without adjustment in either SPI mode (CPOL = 0, CPHA = 0) or (CPOL = 1, CPHA = 1). No mode bit is required to select between the two modes since the interface uses the rising edge of the clock in both modes. The two clocking modes are illustrated in Figure 14. Note that the inactive SCLK value is different for the two modes. Figure 14 illustrates the full-duplex mode, where data is simultaneously clocked into and out of the MAX3420E.
SCLK (Serial Clock)
The SPI master provides the MAX3420E SCLK signal to clock the SPI interface. SCLK has no low-frequency limit, and can be as high as 26MHz. The MAX3420E changes its output data (MISO) on the falling edge of SCLK and samples input data (MOSI) on the rising edge of SCLK. The MAX3420E ignores SCLK transitions when SS is high. The inactive level of SCLK may be low or high, depending on the SPI operating mode (Figure 14).
SS (Slave Select)
The MAX3420E SPI interface is active only when SS is low. When SS is high, the MAX3420E tri-states the SPI output pin and resets the internal MAX3420E SPI logic.
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15
USB Peripheral Controller with SPI Interface MAX3420E
SPI Half- and Full-Duplex Operation
The MAX3420E can be programmed to operate in halfduplex (a bidirectional data pin) or full-duplex (one data-in and one data-out pin) mode. The SPI master sets a register bit called FDUPSPI (full-duplex SPI) to 1 for full-duplex, and 0 for half-duplex operation. Halfduplex is the power-on default. Full-Duplex Operation When the SPI master sets FDUPSPI = 1, the SPI interface uses separate data pins, MOSI and MISO to transfer data. Because of the separate data pins, bits can be simultaneously clocked into and out of the MAX3420E. The MAX3420E makes use of this feature by clocking out 8 USB status bits as the command byte is clocked in, as illustrated in Figure 15. Reading from the SPI Slave Interface (MISO) in Full-Duplex Mode In full-duplex mode the SPI master reads data from the MAX3420E slave interface using the following steps: (1) When SS is high, the MAX3420E is unselected and tri-states the MISO output. (2) After driving SCLK to its inactive state, the SPI master selects the MAX3420E by driving SS low. The MAX3420E turns on its MISO output buffer and places the first data bit (Q7) on the MISO output (Figure 14). (3) The SPI master simultaneously clocks the command byte into the MAX3420E MOSI pin, and USB status bits out of the MAX3420E MISO pin on the rising edges of the SCLK it supplies. The MAX3420E changes its MISO output data on the falling edges of SCLK. (4) After eight clock cycles, the master can drive SS high to deselect the MAX3420E, causing it to tristate its MISO output. The falling edge of the clock puts the MSB of the next data byte in the sequence on the MISO output (Figure 14). (5) By keeping SS low, the master clocks register data bytes out of the MAX3420E by continuing to supply SCLK pulses (burst mode). The master terminates the transfer by driving SS high. The master must ensure that SCLK is in its inactive state at the beginning of the next access (when it drives SS low). In full-duplex mode, the MAX3420E ignores data on MOSI while clocking data out on MISO. Writing to the SPI Slave Interface (MOSI) in Full-Duplex Mode In full-duplex mode, the SPI master writes data to the MAX3420E slave interface through the following steps: (1) The SPI master sets the clock to its inactive state. While SS is high, the master can drive the MOSI pin. (2) The SPI master selects the MAX3420E by driving SS low and placing the first data bit to write on the MOSI input. (3) The SPI master simultaneously clocks the command byte into the MAX3420E and USB status bits out of the MAX3420E MISO pin on the rising edges of the SCLK it supplies. The SPI master changes its MOSI input data on the falling edges of SCLK. (4) After eight clock cycles, the master can drive SS high to deselect the MAX3420E. (5) By keeping SS low, the master clocks data bytes into the MAX3420E by continuing to supply SCLK pulses (burst mode). The master terminates the transfer by driving SS high. The master must ensure that SCLK is inactive at the beginning of the next access (when it drives SS low). In full-duplex mode, the MAX3420E outputs USB status bits on MISO during the first 8 bits (the command byte), and subsequently outputs zeroes on MISO as the SPI master clocks bytes into MOSI. Half-Duplex Operation The MAX3420E is put into half-duplex mode at poweron, or when the SPI master clears the FDUPSPI bit. In half-duplex mode, the MAX3420E tri-states its MISO pin and makes the MOSI pin bidirectional, saving a pin in the SPI interface. The MISO pin can be left unconnected in half-duplex operation. Because of the single data pin, the USB status bits available in full-duplex mode are not available as the SPI master clocks in the command byte. In half-duplex mode these status bits are accessed in the normal way, as register bits. The SPI master must operate the MOSI pin as bidirectional. It accesses a MAX3420E register as follows: (1) The SPI master sets the clock to its inactive state. While SS is high, the master can drive the MOSI pin to any value. (2) The SPI master selects the MAX3420E by driving SS low and placing the first data bit (MSB) to write on the MOSI input. (3) The SPI master turns on its output driver and clocks the command byte into the MAX3420E on the rising edges of the SCLK it supplies. The SPI master changes its MOSI data on the falling edges of SCLK. (4) After eight clock cycles, the master can drive SS high to deselect the MAX3420E.
16
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USB Peripheral Controller with SPI Interface MAX3420E
SS SPI MODE 0,0 (CPOL = 0, CPHA = 0)
MISO
SUSPIRQ
URESIRQ
SUDAVIRQ
IN3BAVIRQ
IN2BAVIRQ
OUT1DAVIRQ OUT0DAVIRQ
IN0BAVIRQ
X
SCLK
MOSI
REG4
REG3
REG2
REG1
REG0
0
DIR
ACKSTAT
Figure 15. SPI Port in Full-Duplex Mode
(5) To write SPI data, the SPI master keeps its output driver on and clocks subsequent bytes into the MOSI pin. To read SPI data, after the eighth clock cycle the SPI master tri-states its output driver and begins clocking in data bytes from the MOSI pin. (6) The SPI master terminates the SPI cycle by returning SS high. Figures 8 and 9 show timing diagrams for full- and halfduplex operation.
Power Management
According to USB rev. 2.0 specification, when a USB host stops sending traffic for at least 3 milliseconds to a peripheral, the peripheral must enter a power-down state called SUSPEND. Once suspended, the peripheral must have enough of its internal logic active to recognize when the host resumes signaling, or if enabled for remote wakeup, that the SPI master wishes to signal a resume event. The following sections titled Suspend and Wakeup and USB Resume describe how the SPI master coordinates with the MAX3420E to accomplish this power management. Suspend After three milliseconds of USB bus inactivity, a USB peripheral is required to enter the USB suspend state and draw no more than 500A of supply current. To accomplish this, after three milliseconds of USB bus inactivity, the MAX3420E sets the SUSPIRQ bit in the USBIRQ (R13) register and asserts the INT output, if SUSPIE = 1 and IE = 1. The SPI master must do any necessary power-saving housekeeping and then set the PWRDOWN bit in the USBCTL (R15) register. This instructs the MAX3420E to enter a power-down state, in which it does the following: * Stops the 12MHz oscillator * Keeps the INT output active (according to the mode set in the PINCTL (R17) register) * Monitors the USB D+ line for bus activity * Monitors the SPI port for any traffic Note that the MAX3420E does not automatically enter a power-down state after three milliseconds of bus inactivity. This allows the SPI master to perform any
17
USB Serial-Interface Engine
The serial-interface engine (SIE) does most of the detailed work required by USB protocol: * USB packet PID detection and checking * CRC check and generation * Automatic retries in case of errors * USB packet generation * NRZI data encoding and decoding * Bit stuffing and unstuffing * Various USB error condition detection * USB bus reset, suspend, and wake-up detection * USB resume signaling * Automatic flow control (NAK) PLL An internal PLL multiplies the 12MHz oscillator signal by four to produce an internal 48MHz clock. When the chip is powered down, the oscillator is turned off to conserve power. When repowered, the oscillator and PLL require time to stabilize and lock. The OSCOKIRQ interrupt bit is used to indicate to the SPI master that the clocking system is stable and ready for operation.
______________________________________________________________________________________
USB Peripheral Controller with SPI Interface MAX3420E
preshutdown tasks before it requests the MAX3420E to enter the power-down state by setting PWRDOWN = 1. Wakeup and USB Resume The MAX3420E may wake up in three ways while it is in the power-down state: (1) The SPI master clears the PWRDOWN bit in the USBCTL (R15) register (this is also achieved by a chip reset). (2) The SPI master signals a USB remote wakeup by setting the SIGRWU bit in the USBCTL (R15) register. When SIGRWU = 1, the MAX3420E restarts the oscillator and waits for it to stabilize. After the oscillator stabilizes, the MAX3420E drives RESUME signaling (a 10ms K-state) on the bus. The MAX3420E times this interval to relieve the SPI master of having to keep accurate time. The MAX3420E also ensures that the RESUME signal begins only after at least 5ms of the bus idle state. When the MAX3420E finishes its RESUME signaling, it sets the RWUDNIRQ (remote-wakeup-done interrupt request) interrupt flag in the USBIRQ (R13) register. At this time the SPI master should clear the SIGRWU bit. (3) The host resumes bus activity. To enable the MAX3420E to wake up from host signaling, the SPI master sets the HOSCSTEN (host oscillator start enable) bit of the USBCTL (R15) register. While in this mode, if the MAX3420E detects a 1 to 0 transition on D+, the MAX3420E restarts the oscillator and waits for it to stabilize. Chip Reset Pulling the RES pin low or setting CHIPRES = 1 clears most of the bits that control USB operation, but keeps the SPI and pin-control bits unchanged so the interface between the SPI master and the MAX3420E is not disturbed. Specifically: * CHIPRES is unchanged. If the SPI master asserted this reset by setting CHIPRES = 1, it removes the reset by writing CHIPRES = 0. * CONNECT is unchanged, keeping the device connected if CONNECT = 1. * The general-purpose outputs GPOUT3-GPOUT0 are unchanged, preventing output glitches. * The GPX output selector (GPXB, GPXA) is unchanged. * The bits that control the SPI interface are unchanged: FDUPSPI, INTLEVEL, and POSINT. * The bits that control power-down and wakeup behavior are unchanged: HOSCSTEN, PWRDOWN, and SIGRWU. All other bits except the three noted in the Power-On Reset section are cleared. Note: The IRQ and IE bits are cleared using this reset. This means that firmware routines that enable interrupts should be called after a reset of this type. USB Bus Reset When the MAX3420E detects 21.33s of SE0, it asserts the URESIRQ bit and clears certain bits. This reset is the least inclusive of the three resets. It maintains the bit states listed in the Power-On Reset and Chip Reset sections, plus it leaves the following bits in their previous states: * Registers R0-R4 are unchanged. The actual data in the FIFOs is never cleared. * The IE bit is unchanged. * URESIE, URESIRQ, URESDNIE, and URESDNIRQ are unchanged, allowing the SPI master to check the state of USB bus resets. As with the chip reset, most of the interrupt request and interrupt enable bits are cleared, meaning that the device firmware must reenable individual interrupts after a bus reset. The exceptions are the interrupts associated with the actual bus reset, allowing the SPI master to detect the beginning and end of the host signaling USB bus reset.
Device Reset
The MAX3420E has three reset mechanisms: * Power-On Reset. This is the most inclusive reset (sets all internal register bits to a known state). * Chip Reset. The SPI master can assert a chip reset by setting the bit CHIPRES = 1, which has the same effect as pulling the RES pin low. This reset clears only some register bits and leaves others alone. * USB Bus Reset. A USB bus reset is the least inclusive (clears the smallest number of bits). Power-On Reset At power-on, all register bits except three are cleared. The following three bits are set to 1 to indicate that the IN FIFOs are available for loading by the SPI master (BAV = buffer available): * IN3BAVIRQ * IN2BAVIRQ * IN0BAVIRQ
18
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USB Peripheral Controller with SPI Interface MAX3420E
3.3V REGULATOR MAX6349TL 1.0F CERAMIC 10k 4.7F 0.1F 12MHz
CXI
CXO
VCC VBUS USB "B" CONNECTOR GND VBCOMP GPI D+ 33 DDRES 33 D+
VL
XI
XO INT MOSI MISO SCLK SS
P
MAX3420E
GND
GPIN GPOUT
4
4
Figure 16. MAX3420E in a Bus-Powered Application
MAX3420E in a Bus-Powered Application
Figure 16 depicts the MAX3420E in a peripheral device that is powered by VBUS. This configuration is advantageous because it requires no external power supply. VBUS is specified from 4.75V to 5.25V, so a 3.3V regulator is required to power the MAX3420E. This diagram assumes that the microprocessor is powered by 3.3V as well, so the VL pin (logic-level reference voltage) is connected to VCC. Therefore, the GPIO (general-purpose inputs/outputs) are referenced to 3.3V. USB is a hot-plug system (VBUS is hot when the device is plugged in), so it is good design practice to use a power-on reset circuit to provide a clean reset to the system when the device is plugged in. The MAX6349TL serves as an excellent USB regulator, since it has very low quiescent current and a POR circuit built in. Because this design is bus powered, it is not necessary to test for the presence of VBUS. In this case, the bus voltage-detection input, VBCOMP, makes an excellent general-purpose input when pulled up to V L . The VBCOMP input has two interrupts associated with it, VBUSIRQ and NOVBUSIRQ. These interrupts can detect both edges of any transitions on the VBCOMP input.
The configuration in Figure 16 shows the SPI interface using the maximum number of SPI interface pins. The data pins, MOSI and MISO, are separate, and the MAX3420E supplies an interrupt signal through the INT output pin to the P to notify the P when its attention is required.
MAX3420E in a Self-Powered Application
Figure 17 shows a self-powered design in which the P has its own power source. This is a common configuration in battery-powered handheld devices. Figure 17 also illustrates the SPI interfacing with the minimum number of pins. This is achieved by using a single bidirectional data line and no interrupt pin connection. The MAX3420E register bit, FDUPSPI, configures the SPI interface for bidirectional operation. Although Figure 17 shows VL = VCC, if the microcontroller uses a different interface voltage (1.71V to 3.6V) this reference voltage can be connected to VL. Figure 17 shows a connection from the MAX3420E GPX output to the microcontroller. GPX can be programmed (see Table 3) to connect the output of the internal VBUS comparator to the GPX output. This enables the microprocessor to detect a USB plug-in event even if the MAX3420E is put into its power-down state.
19
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USB Peripheral Controller with SPI Interface MAX3420E
+3.3V 12MHz 1.0F CERAMIC 0.1F
CXI
CXO
VCC VBUS USB "B" CONNECTOR GND VBCOMP 1.0F CERAMIC D+ 33 DDRES 33 D+
VL
XI
XO GPX INT MOSI MISO SCLK SS N.C. P N.C.
MAX3420E
GND
GPIN 4
GPOUT 4
GPIO
Figure 17. MAX3420E in a Self-Powered Application
The V BUS detect input, VBCOMP, is an important MAX3420E feature. Because the P is powered whether the USB device is plugged in or not, it needs some way to detect a plug-in event. A comparator inside the MAX3420E checks for a valid VBUS connection on VBCOMP and provides a connect status bit to the P. Once connected, the P can delay the logical connection to the USB bus to perform any required initialization, and then connect by setting the CONNECT bit to 1 in the MAX3420E register USBCTL (R15). This connects the internal 1.5k resistor from D+ to VCC, to signal the host that a device has been plugged in. If a host turns off VBUS while the device is connected, the USB rev. 2.0 specification requires that the device must not power its 1.5k pullup resistor connected to D+. The MAX3420E has two features to help service this event. First, the NOVBUSIRQ bit indicates the loss of VBUS. Second, the P can set a bit called VBGATE (VBUS gate) to instruct the MAX3420E to disconnect the pullup resistor anytime VBUS goes away, regardless of the CONNECT bit setting.
Crystal Selection
The MAX3420E requires a crystal with the following specifications: Frequency: 12MHz 0.25% CLOAD: 18pF CO: 7pF max Drive level: 200W Series resonance resistance: 60 max Note: Series resonance resistance is the resistance observed when the resonator is in the series resonant condition. This is a parameter often stated by quartz crystal vendors and is called R1. When a resonator is used in the parallel resonant mode with an external load capacitance, as is the case with the MAX3420E oscillator circuit, the effective resistance is sometimes stated. This effective resistance at the loaded frequency of oscillation is: R1 x ( 1 + (CO / CLOAD))2 For typical CO and CLOAD values, the effective resistance can be greater than R1 by a factor of 2.
20
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USB Peripheral Controller with SPI Interface
ESD Protection
D+, D-, and VBCOMP possess extra protection against static electricity to protect the devices up to 15kV. The ESD structures withstand high ESD in all operating modes: normal operation, suspend mode, and powered down. VBCOMP and V CC require 1F ceramic capacitors connected to ground as close to the pins as possible. D+, D-, and VBCOMP provide protection to the following limits: * 15kV using the Human Body Model * 8kV using the Contact Discharge method specified in IEC 61000-4-2 * 12kV using the IEC 61000-4-2 Air Gap Method
MAX3420E
RC 1M CHARGE-CURRENTLIMIT RESISTOR HIGHVOLTAGE DC SOURCE
RD 1.5k DISCHARGE RESISTANCE DEVICE UNDER TEST
Cs 100pF
STORAGE CAPACITOR
Figure 18. Human Body ESD Test Models
ESD Test Conditions
ESD performance depends on a variety of conditions. Contact Maxim for a reliability report that documents test setup, test methodology, and test results.
IP 100% 90% AMPERES 36.8% 10% 0 0 tRL TIME tDL CURRENT WAVEFORM Ir PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE)
Human Body Model
Figure 18 shows the Human Body Model, and Figure 19 shows the current waveform generated when discharged into a low impedance. This model consists of a 100pF capacitor charged to the ESD voltage of interest, which then discharges into the test device through a 1.5k resistor.
IEC 61000-4-2
The IEC 61000-4-2 standard covers ESD testing and performance of finished equipment. It does not specifically refer to integrated circuits. The major difference between tests done using the Human Body Model and IEC 61000-4-2 is a higher peak current in IEC 61000-42, due to lower series resistance. Hence, the ESD withstand voltage measured to IEC 61000-4-2 generally is lower than that measured using the Human Body Model. Figure 20 shows the IEC 61000-4-2 model. The Contact Discharge method connects the probe to the device before the probe is charged. The Air-Gap Discharge test involves approaching the device with a charged probe.
Figure 19. Human Body Model Current Waveform
RC 50M to 100M CHARGE-CURRENTLIMIT RESISTOR HIGHVOLTAGE DC SOURCE
RD 330 DISCHARGE RESISTANCE DEVICE UNDER TEST
Cs 150pF
STORAGE CAPACITOR
Short-Circuit Protection
The MAX3420E withstands VBUS shorts to D+ and Don the USB connector side of the 33 series resistors.
Figure 20. IEC 61000-4-2 ESD Test Model
Chip Information
PROCESS: BiCMOS
______________________________________________________________________________________
21
USB Peripheral Controller with SPI Interface MAX3420E
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) 24L QFN THIN.EPS
PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm
21-0139
E
1 2
22
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USB Peripheral Controller with SPI Interface
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
MAX3420E
PACKAGE OUTLINE, 12, 16, 20, 24, 28L THIN QFN, 4x4x0.8mm
21-0139
E
2 2
______________________________________________________________________________________
23
USB Peripheral Controller with SPI Interface MAX3420E
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE, 32/48L LQFP, 7x7x1.4mm
21-0054
F
1
2
24
______________________________________________________________________________________
32L/48L,LQFP.EPS
USB Peripheral Controller with SPI Interface MAX3420E
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE, 32/48L LQFP, 7x7x1.4mm
21-0054
F
2
2
Revision History
Pages changed at Rev 2: 4, 5, 19, 20, 22, 23, 24, 25
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.
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