Data Sheet 29319.35 3974 ENABLE1 NC OUT1B 41 40 GND 44 42 GND 1 LOAD 43 SUPPLY1 SENSE1 GND 2 4 3 NC NC 5 OUT1A 6 DMOS DUAL FULL-BRIDGE PWM MOTOR DRIVER STROBE 8 CLOCK 9 DATA 10 PROGRAM PWM TIMER CHARGE PUMP 7 SERIAL PORT VBB1 NC LOGIC 39 NC 38 CP2 37 CP1 36 CP GND 11 35 GND GND 12 34 GND GND 13 33 GND REF1 14 ÷ 32 OSC REF2 15 ÷ 31 SLEEP 30 VREG 29 NC LOGIC 16 SUPPLY PROGRAM PWM TIMER LOGIC VDD NC 17 OUT2B 28 NC 27 ENABLE2 26 25 GND 24 LOAD SUPPLY2 23 GND 21 GND 22 SENSE2 NC 19 NC 20 OUT2A 18 VBB2 Dwg. PP-073 ABSOLUTE MAXIMUM RATINGS at TA = +25°C Load Supply Voltage, VBB ............................ 50 V Output Current, IOUT .................................. ±1.5 A Logic Supply Voltage, VDD .......................... 7.0 V Logic Input Voltage Range, VIN Continous ................... -0.3 V to VDD + 0.3 V tW < 30 ns ................... -1.0 V to VDD + 1.0 V Reference Voltage, VREF ................................. 3 V Sense Voltage (dc), VS Continous .............................................. 0.5 V tW < 1 µs ................................................ 2.5 V Package Power Dissipation, PD .................. 3.9 W Operating Temperature Range, TA ......................................... -20°C to +85°C Junction Temperature, TJ ......................... +150°C Storage Temperature Range, TS ....................................... -55°C to +150°C Output current rating may be limited by duty cycle, ambient temperature, and heat sinking. Under any set of conditions, do not exceed the specified current rating or a junction temperature of 150°C. Designed for pulse-width modulated (PWM) current control of two dc motors, the A3974SED is capable of output currents to ±1.5 A and operating voltages to 50 V. Internal fixed off-time PWM current-control timing circuitry can be programmed via a serial interface to operate in slow, fast, and mixed current-decay modes. Independant ENABLE input terminals are provided for use in controlling the speed and torque of each dc motor with externally applied PWM control signals. Synchronous rectification circuitry allows the load current to flow through the low rDS(on) of the DMOS output driver during the current decay. This feature will eliminate the need for external clamp diodes in most applications, saving cost and external component count, while minimizing power dissipation. Internal circuit protection includes thermal shutdown with hysteresis, undervoltage monitoring of VDD and the charge pump, and crossover-current protection. Special power-up sequencing is not required. The A3974SED is supplied in a 44-lead plastic PLCC with four copper batwing tabs for maximum heat dissipation. The power tabs are at ground potential and need no electrical isolation. FEATURES ■ ±1.5 A, 50 V Continuous Output Rating ■ Low rDS(on) DMOS Output Drivers ■ Programmable Slow, Fast, and Mixed Current-Decay Modes ■ Serial-Interface Controls Chip Functions ■ Synchronous Rectification for Low Power Dissipation ■ Internal UVLO and Thermal Shutdown Circuitry ■ Crossover-Current Protection ■ Sleep and Idle Modes Always order by complete part number: A3974SED . 3974 DMOS DUAL FULL-BRIDGE PWM MOTOR DRIVER FUNCTIONAL BLOCK DIAGRAM VBB1 VDD UNDERVOLTAGE & FAULT DETECT CP CP1 CHARGE PUMP BANDGAP VDD CREG TSD CP2 + LOGIC SUPPLY LOAD SUPPLY1 CHARGE PUMP BANDGAP REGULATOR VREG ENABLE1 OUT1A GATE DRIVE PHASE SYNC RECT MODE SYNC RECT DISABLE MODE CONTROL LOGIC OUT1B SENSE1 CS1 ZERO CURRENT DETECT FIXED OFF PROGRAMMABLE BLANK DECAY RS1 PWM TIMER CURRENT SENSE OSC CLOCK DATA STROBE PHASE ENABLE SYNC RECT MODE SYNC RECT DISABLE PWM MODE INT PWM MODE EXT ENABLE2 REF1 VREF LOAD SUPPLY2 CHARGE PUMP + VBB2 OUT2A GATE DRIVE FIXED OFF BLANK DECAY PROGRAMMABLE PWM TIMER SLEEP MODE REFERENCE BUFFER & DIVIDER SERIAL PORT OUT2B CONTROL LOGIC SENSE2 TO PWM TIMER CS2 ZERO CURRENT DETECT RS2 CURRENT SENSE REFERENCE BUFFER & DIVIDER REF2 VREF2 Dwg. FP-048-1 2 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 2001 Allegro MicroSystems, Inc. 3974 DMOS DUAL FULL-BRIDGE PWM MOTOR DRIVER ELECTRICAL CHARACTERISTICS at TA = +25°C, VBB = 50 V, VDD = 5.0 V, fPWM < 50 kHz (unless otherwise noted). Characteristic Symbol Test Conditions Min. Limits Typ. Max. Units Output Drivers Load Supply Voltage Range Output Leakage Current Output ON Resistance Body Diode Forward Voltage Load Supply Current VBB IDSS rDS(on) VF IBB Operating 15 — 50 V During sleep mode 0 — 50 V VOUT = VBB — <1.0 20 µA VOUT = 0 V — <-1.0 -20 µA Source driver, IOUT = -1.5 A — 0.5 0.55 Ω Sink driver, IOUT = 1.5 A — 0.315 0.35 Ω Source diode, IF = 1.5 A — — 1.2 V Sink diode, IF = 1.5 A — — 1.2 V fPWM < 50 kHz — 4.0 7.0 mA Charge pump on, outputs disabled — 2.0 5.0 mA Sleep or idle mode — — 20 µA Operating 4.5 5.0 5.5 V Control Logic Logic Supply Voltage Range VDD Logic Input Voltage VIN(1) 2.0 — — V VIN(0) — — 0.8 V Logic Input Current (except ENABLE) IIN(1) VIN = 2.0 V — <1.0 ±20 µA IIN(0) VIN = 0.8 V — <1.0 ±20 µA ENABLE Input Current IEN(1) VEN = 2.0 V — 40 100 µA IEN(0) VEN = 0.8 V — 16 30 µA OSC Input Frequency fOSC 2.9 — 6.1 MHz OSC Input Duty Cycle — 40 — 60 % OSC Input Hysterisis ∆VIN 200 — 400 mV Reference Input Voltage Range VREF 0 — 2.6 V Operating continued next page ... www.allegromicro.com 3 3974 DMOS DUAL FULL-BRIDGE PWM MOTOR DRIVER ELECTRICAL CHARACTERISTICS at TA = +25°C, VBB = 50 V, VDD = 5.0 V, fPWM < 50 kHz (unless otherwise noted), continued. Characteristic Control Logic (continued) Symbol Reference Input Current IREF Reference Input Offset Voltage VIO Reference Divider Ratio Gain (Gm) Error (note 3) Propagation Delay Time Crossover Delay Time VREF/VS EG tpd tCOD Test Conditions Min. Units — — ±1.0 µA — ±10 — mV D16 = 1 — 10 — — D16 = 0 — 5.0 — — VREF = 2.6 V, D16 = 0 — 0 ±4.0 % VREF = 0.5 V, D16 = 0 — 0 ±14 % VREF = 2.6 V, D16 = 1 — 0 ±4.0 % VREF = 0.5 V, D16 = 1 — 0 ±10 % 50% TO 90%: PWM change to source on PWM change to source off PWM change to sink on PWM change to sink off 600 50 600 50 750 150 750 150 1000 350 1000 350 ns ns ns ns SR enabled 300 600 1000 ns VREF = 2.6 V Thermal Shutdown Temperature TJ — 165 — °C Thermal Shutdown Hysteresis ∆TJ — 15 — °C 3.9 4.2 4.45 V 0.05 0.10 — V fPWM < 50 kHz — — 10 mA Outputs off — — 8.0 mA Idle mode (D18 = 1, D19 = 0) — — 1.5 mA Sleep mode (inputs below 0.5 V) — — 100 µA UVLO Enable Threshold VUVLO UVLO Hysteresis ∆VUVLO Logic Supply Current IDD Increasing VDD NOTES: 1. Typical Data is for design information only. 2. Negative current is defined as coming out of (sourcing) the specified device terminal. 3. EG = [(VREF/Range) - VS]/(VREF/Range). 4 Limits Typ. Max. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 3974 DMOS DUAL FULL-BRIDGE PWM MOTOR DRIVER FUNCTIONAL DESCRIPTION Serial Interface. The A3974SED is controlled via a 3-wire (clock, data,strobe) serial port. The programmable functions allow maximum flexibility in configuring the PWM to the motor drive requirements. The serial data is written as two 20bit words: 1 bit to select the word and 19 bits of data. The data is clocked in starting with D19. D2 – D6 Fixed Off Time. This five-bit word sets the fixed off-time for the internal PWM control circuitry. The off-time is defined by Word 0 Bit Assignments For example, with an oscillator frequency of 4 MHz, the fixed off-time will be adjustable from 1.75 µs to 63.75 µs in increments of 2 µs. Select Word 0 (D18 = 0) Bit Function D0 Bridge 1 blank time LSB D1 Bridge 1 blank time MSB D2 Bridge 1 off-time LSB D3 Bridge 1 off-time bit 1 D4 Bridge 1 off-time bit 2 D5 Bridge 1 off-time bit 3 D6 Bridge 1 off-time MSB D7 Bridge 1 fast-decay time bit LSB D8 Bridge 1 fast-decay time bit 1 D9 Bridge 1 fast-decay time bit 2 D10 Bridge 1 fast-decay time MSB D11 Bridge 1 sync. rect. control D12 Bridge 1 sync. rect. control D13 Bridge 1 external PWM mode D14 Bridge 1 enable D15 Bridge 1 phase D16 Bridge 1 reference range select D17 Bridge 1 internal PWM mode D18 Word select = 0 D19 Test mode D0 – D1 Blank Time. The current-sense comparator is blanked when any output driver is switched on, according to the table below. fosc is the oscillator input frequency. D1 0 0 1 1 D0 0 1 0 1 Blank Time 4/fOSC 6/fOSC 12/fOSC 24/fOSC toff =(8 [1 + N]/fOSC) - 1/fOSC where N = 0 .... 31 D7 – D10 Fast Decay Time. This four-bit word sets the fastdecay portion of the fixed off-time for the internal PWM control circuitry. This will only have impact if mixed-decay mode is selected (via bit D17). For tfd > toff, the device will effectively operate in fast-decay mode. The fast-decay portion is defined by tfd = (8[1 + N]/fOSC] - 1/fOSC where N = 0 .... 15 For example, with an oscillator frequency of 4 MHz, the fastdecay time will be adjustable from 1.75 µs to 31.75 µs in increments of 2 µs. D11 – D12 Synchronous Rectification. D12 0 0 1 1 D11 0 1 0 1 Synchronous Rectifier Disabled Low side only Active Passive The different modes of operation are described in the synchronous rectification section of the functional description. D13 External PWM Decay Mode. This bit determines the current-decay mode when using ENABLE chopping for external PWM current control. D13 0 1 Mode Fast Slow continued next page ... www.allegromicro.com 5 3974 DMOS DUAL FULL-BRIDGE PWM MOTOR DRIVER FUNCTIONAL DESCRIPTION (continued) D14 Enable Logic. This bit, in conjuction with ENABLE, determines if the output drivers are in the chopped or on state. ENABLE1 0 1 0 1 D14 0 0 1 1 Mode Chopped On On Chopped D15 Phase Logic. This bit determines if the device is operating in the forward or reverse state. D15 State OUTA OUTB 0 1 Reverse Forward L H H L D16 Gm Range Select. This bit determines if VREF is divided by 5 or 10. D16 0 1 Divider ÷10 ÷5 D17 Bridge 2 Mode. This bit determines slow or mixed decay for internal current-control operation. D17 0 1 Decay Mode Mixed Slow D19 Test Mode. This bit is reserved for testing and should never be changed by the user. Default (low) operates the device in normal mode. Word 1 Bit Assignments Select Word 1 (D18 = 1) Bit Function D0 Bridge 2 blank time LSB D1 Bridge 2 blank time MSB D2 Bridge 2 off-time LSB D3 Bridge 2 off-time bit 1 D4 Bridge 2 off-time bit 2 D5 Bridge 2 off-time bit 3 D6 Bridge 2 off-time MSB D7 Bridge 2 fast-decay time bit LSB D8 Bridge 2 fast-decay time bit 1 D9 Bridge 2 fast-decay time bit 2 D10 Bridge 2 fast-decay time bit MSB D11 Bridge 2 sync. rect. control D12 Bridge 2 sync. rect. control D13 Bridge 2 external PWM mode D14 Bridge 2 enable D15 Bridge 2 phase D16 Bridge 2 reference range select D17 Bridge 2 internal PWM mode D18 Word select = 1 D19 Idle mode D0 - D17. Identical definitions as Word 0, with Word 1 selected. Data is written to Full Bridge 2. D19 Idle Mode. The device can be placed in a low-power “idle” mode by writing a “0” to D19. The outputs will be disabled, the charge pump will be turned off, and the device will draw a lower load supply currrent. The undervoltage monitor circuit will remain active. D19 should be programmed high for 1 ms before attempting to enable any output driver. continued next page ... 6 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 3974 DMOS DUAL FULL-BRIDGE PWM MOTOR DRIVER FUNCTIONAL DESCRIPTION (continued) VREG. This internally generated supply voltage is used to operate the sink-side DMOS outputs. VREG is internally monitored and in the case of a fault condition, the outputs of the device are disabled. The VREG terminal should be decoupled with a 0.22 µF capacitor to ground. Charge Pump. The charge pump is used to generate a supply voltage greater than VBB to drive the source-side DMOS gates. A 0.22 µF ceramic capacitor should be connected between CP1 and CP2 for pumping purposes. A 0.22 µF ceramic capacitor should be connected between VCP and VBB to act as a reservoir to run the high-side DMOS devices. The CP voltage is internally monitored and in the case of a fault condition, the outputs of the device are disabled. Shutdown. In the event of a fault due to excessive junction temperature, or low voltage on CP or VREG, the outputs of the device are disabled until the fault condition is removed. At power up, or in the event of low VDD, the UVLO circuit disables the drivers and resets the data in the serial port to all zeros. Current Regulation. Load current is regulated by an internal fixed off-time PWM control circuit. When the outputs of the DMOS H-bridge are turned on, the current increases in the motor winding until it reaches a trip value determined by the external sense resistor (RS), the applied analog reference voltage (VREF), and serial data bit D16: When D16 = 0 ....................... ITRIP = VREF/10RS When D16 = 1 ....................... ITRIP = VREF/5RS At the trip point, the sense comparator resets the source-enable latch, turning off the source driver (except in the case of lowside only mode where the sink driver is turned off). The load inductance then causes the current to recirculate for the serialport programmed fixed off-time period. The current path during recirculation is determined by the configuration of slow/ mixed-decay mode (D17) and the synchronous rectification control bits (D11 and D12). www.allegromicro.com Sleep Mode. The input terminal SLEEP is dedicated to putting the device into a minimum current draw mode. When asserted low, the serial port will be reset to all zeros and all circuits will be disabled. PWM Timer Function. The PWM timer is programmable via the serial port (bits D2 – D10) to provide fixed off-time PWM signals to the control circuitry. In mixed current-decay mode, the first portion of the off time operates in fast decay, until the fast-decay time count is reached (serial bits D7 – D10), followed by slow decay for the rest of the off-time period (bits D2 – D6). If the fast-decay time is set longer than the off-time, the device effectively operates in fast-decay mode. Bit D17 selects mixed or slow decay. Synchronous Rectification. When a PWM off cycle is triggered, either by an ENABLE chop command or internal fixed off-time cycle, load current will recirculate according to the decay mode selected by the control logic. After a short crossover delay, the A3974 synchronous rectification feature will turn on the appropriate MOSFET (or pair of MOSFETs for the mixed decay portion of the off-time) during the current decay and effectively short out the body diodes with the low rDS(on) driver. This will lower power dissipation significantly and can eliminate the need for external Schottky diodes. Synchronous rectification can be configured in active mode, passive mode, low side only, or disabled via the serial port (bits D11 and D12). The active mode prevents reversal of load current by turning off synchronous rectification when a zero current level is detected. Passive mode will allow reversal of current but will turn off the synchronous rectifier circuit if the load current inversion ramps up to the current limit set by VREF/10RS (when D16 = 0) or VREF/5RS(when D16 = 1). Low side only mode will switch the low-side MOSFETs on during the off time to short out the current path through the MOSFET body diode. With this setting, the high-side MOSFETs will not synchronously rectify so four external diodes from output to supply are recommended. This mode is intended for use with high-power applications where it is desired to save the expense of two external diodes per bridge. In this mode, the sink-side MOSFETs are chopped during the PWM off time. In all other cases, the source-side MOSFETs are chopped in response to a PWM OFF command. 7 3974 DMOS DUAL FULL-BRIDGE PWM MOTOR DRIVER APPLICATIONS INFORMATION Current Sensing. To minimize inaccuracies in sensing the ITRIP current level caused by ground-trace IR drops, the sense resistor should have an independent ground return to a ground terminal of the device. For low-value sense resistors, the IR drops in the PCB sense traces of the resistor can be significant and should be taken into account. The use of sockets should be avoided as they can introduce variation in RS due to their contact resistance. The maximum value of RS is given as RS = 0.5/ITRIPMAX. Braking. The braking function is implemented by driving the device in slow-decay mode via serial port bit D13, enabling synchronous rectification via bits D11 and D12, and applying an enable chop command with the combination of D14 and the ENABLE input terminal. Because it is possible to drive current in both directions through the DMOS switches, this configuration effectively shorts out the motor-generated BEMF as long as the ENABLE chop mode is asserted. It is important to note that the internal PWM current-control circuit will not limit the current when braking, because the current does not flow through the sense resistor. The maximum brake current can be approximated by VBEMF/RL. Care should be taken to ensure that the maximum ratings of the device are not exceeded in worstcase braking situations of high speed and high inertial loads. Thermal protection. Circuitry turns off all drivers when the junction temperature reaches 165°C typically. It is intended only to protect the device from failures due to excessive junction temperatures and should not imply that output short circuits are permitted. Thermal shutdown has a hysteresis of approximately 15°C. Layout. The printed wiring board should use a heavy ground plane. For optimum electrical and thermal performance, the driver should be soldered directly onto the board. The ground side of RS should have an individual path to a ground terminal of the device. This path should be as short as is possible physically and should not have any other components connected to it. The load supply terminal, VBB, should be decoupled with an electrolytic capacitor (>47 µF is recommended) placed as close to the device as is possible. Serial Port Write Timing Operation. Data is clocked into shift register on the rising edge of CLOCK signal. Normally, STROBE will be held high, and only will be brought low to initiate a write cycle. Refer to diagram below and specification table for timing requirements. STROBE C D E F G CLOCK A DATA B D19 D18 D0 Dwg. WP-038 A. Minimum Data Setup Time ........................................... 15 ns B. Minimum Data Hold Time ............................................ 10 ns C. Minimum Setup Strobe to Clock Rising Edge .......... 50 ns D. Minimum Clock High Pulse Width ........................... 50 ns E. Minimum Clock Low Pulse Width ............................ 50 ns F. Minimum Setup Clock Rising Edge to Strobe ........... 50 ns G. Minimum Strobe Pulse Width ................................... 50 ns 8 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 3974 DMOS DUAL FULL-BRIDGE PWM MOTOR DRIVER Terminal List Terminal Name GND SENSE1 NC OUT1A NC STROBE CLOCK DATA GND REF1 REF2 LOGIC SUPPLY NC OUT2A NC SENSE2 GND LOAD SUPPLY2 ENABLE2 NC OUT2B NC VREG SLEEP OSC GND CP CP1 & CP2 NC OUT1B NC ENABLE1 LOAD SUPPLY1 GND www.allegromicro.com Terminal Description Power and logic ground terminals Sense resistor terminal for bridge 1 No (internal) connection DMOS H-bridge 1 – output A No (internal) connection Logic input for serial Interface Logic input for serial Interface Logic input for serial Interface Power and logic ground terminals Gm reference input voltage – bridge 1 Gm reference input voltage – bridge 2 VDD, the low voltage (typically 5 V) supply No (internal) connection DMOS H-bridge 2 – output A No (internal) connection Sense resistor pin for bridge 2 Power and logic ground terminals VBB2, the high current, 20 V to 50 V, supply for bridge 2 Logic input for bridge 2 – enable control No (internal) connection DMOS H-bridge 2 – output B No (internal) connection Regulator decoupling capacitor (typ. 0.22 µF) Logic input for SLEEP mode Logic-level oscillator (square wave) input Power and logic ground terminals Reservoir capacitor (typically 0.22 µF) The charge pump capacitor (typically 0.22 µF) No (internal) connection DMOS H-bridge 1 – output B No (internal) connection Logic input for bridge 1 – enable control VBB1, the high current, 20 V to 50 V, supply for bridge 1 Power and logic ground terminals Terminal Number 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 33, 34, 35 36 37 & 38 39 40 41 42 43 44 9 3974 DMOS DUAL FULL-BRIDGE PWM MOTOR DRIVER Dimensions in Inches (controlling dimensions) 18 28 29 17 0.032 0.026 0.319 0.291 0.695 0.685 0.021 0.013 0.656 0.650 0.319 0.291 0.050 INDEX AREA BSC 7 39 40 0.020 44 1 2 6 0.656 0.650 MIN 0.695 0.685 0.180 0.165 Dwg. MA-005-44A in NOTES: 1. Lead spacing tolerance is non-cumulative. 2. Exact body and lead configuration at vendor’s option within limits shown. 3. Available in standard sticks/tubes of 28 devices or add “TR” to part number for tape and reel. 10 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 3974 DMOS DUAL FULL-BRIDGE PWM MOTOR DRIVER Dimensions in Millimeters (for reference only) 28 18 29 17 0.812 0.661 8.10 7.39 17.65 17.40 0.533 0.331 16.662 16.510 8.10 7.39 INDEX AREA 1.27 BSC 39 7 40 0.51 MIN 4.57 4.20 44 1 2 6 16.662 16.510 17.65 17.40 Dwg. MA-005-44A mm NOTES: 1. Lead spacing tolerance is non-cumulative. 2. Exact body and lead configuration at vendor’s option within limits shown. 3. Available in standard sticks/tubes of 28 devices or add “TR” to part number for tape and reel. www.allegromicro.com 11 3974 DMOS DUAL FULL-BRIDGE PWM MOTOR DRIVER The products described here are manufactured under one or more U.S. patents or U.S. patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro products are not authorized for use as critical components in life-support devices or systems without express written approval. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. 12 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000