Drives N-channel MOSFETs Synchronous rectification power dissipation I

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Drives N-channel MOSFETs Synchronous rectification power dissipation I

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A4931 3-Phase Brushless Motor Pre-Driver
Drives N-channel MOSFETs Synchronous rectification power dissipation Internal UVLO thermal shutdown circuitry Hall element inputs current limiting Dead time protection outputs Standby mode Lock detect protection Overvoltage protection
A4931 complete 3-phase brushless motor pre-driver. device capable driving wide range N-channel power MOSFETs support motor supply voltages Commutation logic determined three Hall-element inputs spaced 120°. Other features include fixed off-time pulse width modulation (PWM) current control limiting inrush current, locked-rotor protection with adjustable delay, thermal shutdown, overvoltage monitor, synchronous rectification. Internal synchronous rectification reduces power dissipation turning appropriate MOSFETs during current decay, thus shorting body diode with RDS(on) MOSFET. Overvoltage protection disables synchronous rectification when motor pumps supply voltage beyond overvoltage threshold during current recirculation. A4931 offers enable, direction, brake inputs that control current using either phase enable chopping. Logic outputs used accurately measure motor rotation. Output signals toggle state during Hall transitions, providing accurate speed output microcontroller speed control circuit. Operating temperature range -20°C 105°C. A4931 supplied 28-terminal package with exposed thermal pad. This small footprint package lead (Pb) free with 100% matte leadframe plating.
Package: 28-contact package)
Approximate Scale
Typical Application
HBIAS SENSE
A4931
System Control Logic BRAKEZ ENABLE
4931-DS, Rev.
A4931
3-Phase Brushless Motor Pre-Driver
Selection Guide
Part Number
A4931METTR-T
Packing
1500 pieces reel
Package
0.90 nominal height
Absolute Maximum Ratings
Characteristic
Load Supply Voltage Motor Phase Output Hall Input Logic Input Voltage Range Operating Ambient Temperature Maximum Junction Temperature Storage Temperature
Symbol
TJ(max) Tstg Range
Notes
Rating
-0.3 -0.3
Units
Thermal Characteristics
Characteristic Symbol Test Conditions*
4-layer based JEDEC standard
Rating
Units
Package Thermal Resistance, Junction Ambient Package Thermal Resistance, Junction Exposed *For additional information, refer Allegro website.
Allegro MicroSystems, Inc. Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
A4931
3-Phase Brushless Motor Pre-Driver
Functional Block Diagram
Lock Detect
CHARGE PUMP VREG
HBIAS HALL HACommunication Logic
Enable
HALL
VREG
HALL HCControl Logic
GATE DRIVE
SENSE RSENSE
BRAKEZ System Logic ENABLE
Terminal List
Number Name HCGND HBIAS SENSE Hall input Hall input Hall input Hall input Hall input Hall input Ground Hall bias power supply output Charge pump capacitor terminal Charge pump capacitor terminal Supply voltage Reservoir capacitor terminal Sense resistor connection side gate drive Description Number Name ENABLE BRAKEZ Description side gate drive side gate drive High side gate drive High side source connection High side gate drive High side source connection High side gate drive High side source connection speed control output inputs) speed control output input) Locked rotor detect timing capacitor Logic input motor direction Logic input external control Logic input motor brake (active low)
Allegro MicroSystems, Inc. Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
A4931
3-Phase Brushless Motor Pre-Driver
ELECTRICAL CHARACTERISTICS* Valid 25°C, unless noted otherwise
Characteristics
Supply Voltage Range Motor Supply Current HBIAS HBIAS Current Limit Control Logic Logic Input Voltage Logic Input Current Input Glitch Reject Standby Pulse Propagation Delay HBIAS Wake-up Delay, Standby Mode Gate Drive High-Side Gate Drive Output Low-Side Gate Drive Output Gate Drive Current (Sourcing) Gate Drive Pull Down Resistance Dead Time Current Limit Input Threshold Fixed Off-Time Protection Thermal Shutdown Temperature Thermal Shutdown Hysteresis UVLO Enable Threshold UVLO Hysteresis UVLO Lock Detect Duration Overvoltage Threshold Hall Logic Hall Input Current Common Mode Input Range Input Voltage Range Hall Threshold Hysteresis Pulse Reject Filter Output Saturation Voltage Leakage Current VFG(sat) IFGlkg IHALL VCMR VHALL VHYS tpulse Difference Hall inputs transition mVp-p TJTSD TJTSDhys VBBUV VBBUVhys VCPUV tlock VBBOV Relative Rising Rising 0.75 7.85 37.5 VGS(H) VGS(L) IGate RGate tdead VREF tOFF Relative VBB, IGATE IGATE 1000 1300 VIN(1) VIN(0) IIN(1) IIN(0) tGLITCH tdENB tdHBIAS DIR, BRAKEZ pins outputs CHBIAS <1.0 <-1.0 1000 1300
Symbol
VHBIAS IHBIASlim Operating
Test Conditions
fPWM kHz, CLOAD 1000 Charge pump outputs disabled, Standby mode IHBIAS
Min.
Typ.
Max.
VBBOV
Units
*Typical data initial design estimations only, assume optimum manufacturing application conditions. Performance vary individual units, within specified maximum minimum limits. input output current specifications, negative current defined coming (sourcing) specified device pin. Specifications throughout allowed operating temperature range guaranteed design characterization.
Allegro MicroSystems, Inc. Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
A4931
Inputs
(Forward) (Reverse) Fault* Fault* Brake* Don't Care
3-Phase Brushless Motor Pre-Driver
Resulting Pre-Driver Outputs BRAKEZ
Logic States Table (See timing charts, below) Don't Care, high impedance
Condition Motor Output
Allegro MicroSystems, Inc. Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
A4931
3-Phase Brushless Motor Pre-Driver
Power-up Standby Modes Timing Diagram
VBBUV
Charge Pump
HBIAS Voltage Standby Mode Turn Hall Bias Supply
tdENB
Outputs Enabled
Outputs Disabled
Outputs Enabled
Power-up Standby Modes Timing Diagram
VBBUV
VBB+7.5 Charge Pump
VCPUV
7.5V HBIAS Voltage
VHBIAS
Outputs Enabled
Outputs Disabled
Allegro MicroSystems, Inc. Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
A4931
3-Phase Brushless Motor Pre-Driver
Functional
Current Regulation Load current regulated internal
fixed off-time control circuit. When outputs full bridge turned current increases motor winding until reaches value, ITRIP given ITRIP RSENSE
blanking function. duration fixed
Synchronous Rectification When PWM-off cycle
triggered, either chop command internal fixed off-time cycle, load current recirculates. A4931 synchronous rectification feature turns appropriate MOSFETs during current decay, effectively shorts body diodes with RDS(on) driver. This lowers power dissipation significantly eliminate need external Schottky diodes.
When ITRIP reached, sense comparator resets source enable latch, turning source driver. this point, load inductance causes current recirculate fixed off-time period.
Enable Logic Enable input terminal (ENB pin) allows
external PWM. turns selected sink-source pair. high switches appropriate drivers load current decays. held low, current will rise until reaches level internal current control circuit. Typically frequency range. high pulse width exceeds gate outputs disabled. Enable logic summarized following table:
Setting typical Outputs Source Chopped Outputs State Drive Slow Decay with Synchronous Rectification Disable
Brake Mode logic BRAKEZ activates Brake
mode. logic high allows normal operation. Braking turns three sink drivers, effectively shorting motor-generated BEMF. BRAKEZ input overrides input also Lock Detect function. important note that internal current control circuit does limit current when braking, because current does flow through sense resistor. maximum current approximated VBEMF RLOAD. Care should taken insure that maximum ratings A4391 exceeded worse case braking situation, high speed high inertial load.
HBIAS Function This function provides power supply
current-limited This reference voltage used power logic sections also power external Hall elements.
Fixed Off-Time A4931 fixed off-time
nominal.
Blank Timer When source driver turns current spike occurs reverse recovery currents clamp diodes well switching transients related distributed capacitance load. prevent this current spike from erroneously resetting source Enable latch, sense comparator blanked. blanking timer runs after off-time counter completes, order provide blanking function. blanking timer reset when chopped changed. With external control, change triggers
Standby Mode prevent excessive power dissipation
current draw external Hall elements, Standby mode turns HBIAS output voltage. Standby mode triggered holding high longer than Note that Brake mode overrides Standby mode, hold BRAKEZ high order enter Standby mode.
Charge Pump internal charge pump used generate
supply above drive high-side MOSFETs. volt-
Allegro MicroSystems, Inc. Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
A4931
3-Phase Brushless Motor Pre-Driver
internally monitored, case fault condition, outputs device disabled.
Hall State Reporting open drain output
that changes state each transition external Hall element. open drain output that changes state each transition.
Fault Shutdown event fault excessive
junction temperature voltage VBB, outputs device disabled until fault condition removed. power-up UVLO circuit disables drivers. These fault conditions latched only cleared following actions: Rising falling edge UVLO threshold exceeded (during power-up cycle) held high tlock
Lock Detect Function will evaluate locked rotor
condition under either these different conditions: signal consistently changing. proper commutation sequence being followed. motor locked condition which toggles between specific Hall device states. Both these fault conditions allowed persist period time, tlock. tlock capacitor connected pin. produces triangle waveform (1.67 peak-to-peak) with frequency linearly related capacitor value. tlock defined cycles this triangle waveform, tlock After wait time, tlock expired, outputs disabled, fault latched. Lock Detect function disabled connecting GND. When A4931 Brake mode, Lock Detect counter disabled.
Overvoltage Protection monitored determine
hazardous voltage present motor generator pumping supply bus. When voltage exceeds VBBOV synchronous rectification feature disabled.
Overtemperature Protection temperature exceeds
approximately 170°C, Thermal Shutdown function will disable outputs until internal temperature falls below 15°C hysteresis.
Allegro MicroSystems, Inc. Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com
A4931
3-Phase Brushless Motor Pre-Driver
Package, 28-Contact
0.30 5.00 ±0.15 1.15 0.50
5.00 ±0.15
3.15 4.80
3.15 0.08 +0.05 0.25 -0.07 0.50 SEATING PLANE 0.90 ±0.10 4.80 Layout Reference View
+0.20 0.55 -0.10
Reference Only (reference JEDEC MO-220VHHD-1) Dimensions millimeters Exact case lead configuration supplier discretion within limits shown 3.15 3.15 Terminal mark area Exposed thermal (reference only, terminal identifier appearance supplier discretion) Reference land pattern layout (reference IPC7351 QFN50P500X500X100-29V1M); pads minimum 0.20 from adjacent pads; adjust necessary meet application process requirements layout tolerances; when mounting multilayer PCB, thermal vias exposed thermal land improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5) Coplanarity includes exposed thermal terminals
Copyright ©2007-2008, Allegro MicroSystems, Inc. products described here manufactured under more U.S. patents U.S. patents pending. Allegro MicroSystems, Inc. reserves right make, from time time, such departures from detail specifications required permit improvements performance, reliability, manufacturability products. Before placing order, user cautioned verify that information being relied upon current. Allegro's products used life support devices systems, failure Allegro product reasonably expected cause failure that life support device system, affect safety effectiveness that device system. information included herein believed accurate reliable. However, Allegro MicroSystems, Inc. assumes responsibility use; infringement patents other rights third parties which result from use. latest version this document, visit website: www.allegromicro.com
Allegro MicroSystems, Inc. Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com

Drives N-channel MOSFETs Synchronous rectification power dissipation I

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