A3938SLDTR - Allegro Microsystems

Description

The A3938 is a three-phase, brushless DC motor controller.

It has a high-current gate drive capability that allows driving

of a wide range of power MOSFETs and can support motor

supply voltages to 50 V. The A3938 integrates a bootstrapped

high-side driver to minimize the external component count

required to drive N-channel MOSFET drivers.

Internal fixed off-time, PWM current-control circuitry can be

used to regulate the maximum load current to a desired value.

The peak load current limit is set by the user’s selection of an

input reference voltage and external sensing resistor. A user-

selected external RC timing network sets the fixed off-time

pulse duration. For added flexibility, the PWM input can provide

speed/torque control where the internal current control circuit

sets a limit on the maximum current.

The A3938 includes a synchronous rectification feature. This

shorts out the current path through the power MOSFET reverse

body diodes during PWM off-cycle current decay. This can

minimize power dissipation in the MOSFETs, eliminate the

need for external power clamp diodes, and potentially allow a

more economical choice for the MOSFET drivers.

The A3938 provides commutation logic for Hall sensors

configured for 120-degree spacing. The H-all input pins are

pulled-up to an internally-generated 5 V reference. Power

MOSFET protection features include: bootstrap capacitor

charging current monitor, regulator undervoltage monitor,

motor lead short-to-ground, and thermal shutdown.

The LD package is lead (Pb) free, with 100% matte tin plated

leadframe.

26301.104H

Features and Benefits

▪ Drives a wide range of N-channel MOSFETs

▪ Low-side synchronous rectification

▪ Power MOSFET protection

▪ Adjustable dead time for cross-conduction protection

▪ Selectable coast or dynamic brake on power-down or

RESET input

▪ Fast/slow current decay modes

▪ Internal PWM current control

▪ Motor lead short-to-ground protection

▪ Internal 5 V regulator

▪ Fault diagnostic output

▪ Thermal shutdown

▪ Undervoltage protection

Three-Phase Power MOSFET Controller

Package 38-pin TSSOP (suffix LD):

A3938

Approximate Scale 1:1

Fault

SENSE

PWM

BRKSEL

BRKCAP

BRAKE

DIR

N/C

GHC

GLB

GHB

GLA

GHA

VREG

LCAP

N/C

FAULT

RESET

GLC

N/C

PGND

AGND

DEAD

REF

N/C

VBB

MODE

N/C

Control

Logic

Three-Phase Power MOSFET Controller

A3938

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Selection Guide

Part Number Packing

A3938SLDTR-T 4000 per reel

Absolute Maximum Ratings

Characteristic Symbol Notes Rating Units

Load Supply Voltage VBB 50 V

VREG Pin, Transient VREG 15 V

Logic Input Voltage Range VIN –0.3 to VLCAP + 0.3 V

Sense Voltage Range VSENSE –5 to 1.5 V

Output Voltage Range V

SA, SB, SC Pins –5 to 50 V

GHA, GHB, GHC Pins –5 to VBB + 17 V

CA, CB, CC Pins VSx + 17 V

Operating Ambient Temperature TARange S –20 to 85 ºC

Junction Temperature TJ150 ºC

Storage Temperature Tstg –55 to 150 ºC

Thermal Characteristics (may require derating at maximum conditions)

Characteristic Symbol Test Conditions Min. Units

Package Thermal Resistance RθJA LD package, 4 layer PCB based on JEDEC standard 51 ºC/W

Three-Phase Power MOSFET Controller

A3938

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Functional Block Diagram

(This diagram shows only one of the three outputs)

VREG

Regulator

VBB

Charge Pump

Dead-Time

Adjust

RC Blanking

Fixed Off-Time

VREG

Low-Side

Driver

High-Side

Protection

Logic

GHA

DEAD

GLA

PGND

MODE

PWM

SENSE

To Phase B

REF

CBOOT

DIR

RESET

BRAKE

To Phase C

Low-Side

Protection

Logic

Turn-On

Delay

LCAP

10 uF

0.1 uF

FAULT

AGND

BRKSEL

BRKCAP

Power Loss

Brake 4.7uF

VREGUVLO

VREG

RESET

Control

Logic

O.D.

Invalid Hall

VREG Undervoltage

Short to GND

TSD

Turn-On

Delay

High-Side

Driver

AFor 12 V applications, VBB must be shorted to VREG. For this condition, the absolute

maximum rating of 15 V on VREG must be maintained to prevent damage to the A3938.

Three-Phase Power MOSFET Controller

A3938

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

ELECTRICAL CHARACTERISTICS1,2 Unless otherwise noted: TA = 25°C, VBB = 18 V to 50 V, CLCAP = 0.1 μF, CBOOT = 0.1 μF,

CVREG = 10 μF, PWM = 22.5 kHz, square wave, two phases active

Characteristics Symbol Test Conditions Min. Typ.1Max. Units

Quiescent Current IVBB RESET = 1, Coast mode, stopped – – 8.0 mA

LCAP Regulator VLCAP Ilcap = –3.0 mA 4.75 5 5.25 V

VREG =VBB Supply Voltage Range VREG VREG = VBB, observe maximum rating = 15 V 10.8 – 13.2 V

VREG Output Voltage VREG

VBB = 13.2 V to 18 V, Ivreg = –10 mA – VBB – 2.5 – V

VBB = 18 V to 50 V, Ivreg = –10 mA 12.4 13 13.6 V

VREG Load Regulation VREGLOAD Ivreg = –1 mA to –30 mA, Coast mode – 25 – mV

VREG Line Regulation VREGLIN Ivreg = –10 mA, Coast mode – 40 – mV

Control Logic

Logic Input Voltage

VIN(1) Minimum high level for logical 1 2.0 – – V

VIN(0) Maximum low level for logical 0 – – 0.8 V

Logic Input Current

IIN(1) VIN = 2.0 V –30 – –90 A

IIN(0) VIN = 0.8 V –50 – –130 A

Gate Drive

Low-Side Drive, Output High VHGL Igx = 0 VREG – 0.8 VREG – 0.5 – V

High-Side Drive, Output High VHGH Igx = 0 10.4 11.6 12.8 V

Pull-Up Switch Resistance RDS(ON) Igx = –50 mA – 14 – 

Pull-Down Switch Resistance RDS(ON) Igx = 50 mA – 4 – 

Low-Side Switching, 10/90 Rise Time trGL Cload = 3300 pF – 120 – ns

Low-Side Switching, 10/90 Fall Time tfGL Cload = 3300 pF – 60 – ns

High-Side Switching, 10/90 Rise Time trGH Cload = 3300 pF – 120 – ns

High-Side Switching, 10/90 Fall Time tfGH Cload = 3300 pF – 60 – ns

Propagation Delay; GHx,GLx Rising Tpr PWM to gate drive out, Cload = 3300 pF – 220 – ns

Propagation Delay; GHx,GLx Falling Tpf PWM to gate drive out, Cload = 3300 pF – 110 – ns

Dead Time, Maximum tDEAD Vdead = 0, GHx to GLx, Cload = 0 3.5 5.6 7.6 s

Dead Time, Minimum tDEAD IDEAD = 780 A, GLx to GHx, Cload = 0 50 100 150 ns

Continued on next page...

Three-Phase Power MOSFET Controller

A3938

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Characteristics Symbol Test Conditions Min. Typ.1Max. Units

Bootstrap Capacitor

Bootstrap Capacitor Voltage VCX Icx = 0, Vsx = 0, Vreg = 13 V 10.4 11.6 12.8 V

Bootstrap ROUT RCX Icx = –50 mA – 9 12 

Charge Current (Source) ICX 100 – – mA

Current Limit Circuitry

Input Offset Voltage VIO 0 V < Vcmr < 1.5 V – – ± 5 mV

Input Current , Sense pin IB0 V < Vcm, Vdiff < 1.5 V – –25 – A

Input Current , Reference pin IB0 V < Vcm, Vdiff < 1.5 V – 0 – A

Blank Time tBLANK R = 56 k, C = 470 pF – 0.91 – s

RC Charge Current IRC –0.9 –1 –1.1 mA

RC Voltage Threshold

VRCL 1.0 1.1 1.2 V

VRCH 2.7 3.0 3.3 V

Protection Circuitry

Bootstrap Charge Threshold Icx GHx turns on, and GLx turns off, at Icx – –9 – mA

Short to Ground, Drain-Source Monitor Vdsh VBB – VSX, high side on 1.3 2.0 2.7 V

VREG Undervoltage Threshold UVLO

VREG increasing 9.2 9.7 10.2 V

VREG decreasing 8.6 9.1 9.6 V

Fault Output Voltage VOUT IOL = 1 mA – – 0.5 V

Brake Capacitor Supply Current IBRAKE VBB = 8 V, BRKSEL = 1 – 30 – A

Low Side Gate Voltage VGLBH VBB=0, BRKCAP = 8V – 6.6 – V

Thermal Shutdown Temperature TJ– 165 – °C

Thermal Shutdown Hysteresis TJ–10– °C

ELECTRICAL CHARACTERISTICS1,2 (continued) Unless otherwise noted: TA = 25°C, VBB = 18 V to 50 V, CLCAP = 0.1 μF,

CBOOT = 0.1 μF, C VREG = 10 μF, PWM = 22.5 kHz, square wave, two phases active

1Typical data are for initial design estimations only, and assume optimum manufacturing and application conditions. Performance may vary for

individual units, within the speciﬁ ed maximum and minimum limits.

2Negative current is deﬁ ned as conventional current coming out of (sourced from) the speciﬁ ed device terminal.

Three-Phase Power MOSFET Controller

A3938

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

RESET. A logic input that enables the device. Has internal

50 kΩ pull-up to LCAP. Setting RESET to 1 coasts or brakes

the motor, depending on the state of the BRKSEL pin. Set-

ting RESET to 0 enables the gate drive to follow commuta-

tion logic. Setting RESET to 1 overrides the BRAKE pin.

GLA/GLB/GLC. Low-side gate drive outputs for external

MOSFET drivers. External series gate resistors can be used

to control slew rate seen at the power driver gate, thereby

controlling the di/dt and dv/dt of Sx outputs.

SA/SB/SC. Directly connected to the motor terminals,

these pins sense the voltages switched across the load. The

pins are also connected to the negative side of the bootstrap

capacitors and the negative supply connections for the ﬂ oat-

ing high-side drivers.

GHA/GHB/GHC. High-side gate drive outputs for

N-channel MOSFET drivers. External series gate resistors

can be used to control slew rate seen at the power driver

gate, thereby controlling the di/dt and dv/dt of Sx outputs.

CA/CB/CC. High-side connections for bootstrap capaci-

tors, providing positive supply for high-side gate drivers. The

bootstrap capacitors are charged to approximately VREG

when the output Sx terminals go low. When the outputs

swing high, the voltages on these pins rise with the outputs to

provide the boosted gate voltages needed for the N-channel

power MOSFETs.

MODE. Logic input to set current-decay mode. In response

to a PWM Off command, Slow Decay mode (MODE = 1)

switches off the high-side FET, and Fast Decay mode

(MODE = 0) switches off the high-side and low-side FETs.

Has an internal 50 kΩ pull-up to LCAP.

H1/H2/H3. Hall sensor inputs with internal, 50 kΩ pull-ups

to LCAP. Conﬁ gured for 120-degree electrical spacing.

DIR. Logic input to reverse rotation (see the table Commu-

tation Truth Table, on the next page). Has internal, 50 kΩ

pull-up to LCAP.

FAULT. Open-drain output to indicate fault condition. Will

be pulled high (usually by 5.1 kΩ external pull-up) for any of

the following fault conditions:

• Invalid Hall sensor input code (coasts the motor).

• Undervoltage condition detected at VREG (coasts or brakes

the motor depending on stored setting for BRKSEL).

• Thermal shutdown (coasts the motor).

• Motor lead (SA/SB/SC) connected to ground (turns off

only the high-side power MOSFETs).

Only the “short-to-ground” fault is latched, but it is cleared

at each commutation. If the motor has stalled due to a short-

to-ground being detected, toggling the RESET pin or repeat-

ing a power-up sequence clears the fault.

BRAKE. Logic input for braking function. Setting BRAKE

to 1 turns on low-side MOSFETs, and turns off the high-side

MOSFETs. This effectively shorts the BEMF in the windings

and brakes the motor. Internal 50 kΩ pull-up to LCAP. Set-

ting RESET to 1 overrides this BRAKE pin. See also BRKSEL.

BRKCAP. This pin is for connection of the reservoir

capacitor used to provide the positive power supply for the

sink drive outputs for a power-down condition. This allows

predictable braking, if desired. Using a 4.7 F capacitor will

provide 6.5 V gate drive for 300 ms. If the power-down brak-

ing option is not needed (i.e., BRKSEL = 0), then this pin

should be tied to VREG.

BRKSEL. Logic input to enable/disable braking upon

power-down condition or RESET = 1. Internal 50 kΩ pull-up

to LCAP. Setting BRKSEL to 0 enables Coast mode. Setting

BRKSEL to 1 enables Brake mode.

PWM. Speed control input. Setting PWM to 1 turns on

MOSFETs selected by Hall input logic. Setting PWM to 0

turns off the selected MOSFETs. Keep the PWM input held

high to utilize internal current control circuitry. Internal

50 kΩ pull-up to LCAP.

RC. Analog input. Connection for RT and CT to set the

ﬁ xed off-time. CT also sets the BLANK time (see the section

Application Information). It is recommended that the ﬁ xed

off-time should not be less than 10 μs. The resistor should be

in the range between 10 kΩ and 500 kΩ.

VREG. Regulated 13 V supply for the low-side gate drive

and the bootstrap capacitor charge circuit. As a regulator, use

a 10 μF decoupling/storage capacitor (ESR < 1 Ω) from this

pin to AGND, as close to the device pins as possible.

Note: For 12 V applications, the VREG pin should be

shorted to VBB.

Pin Descriptions

Three-Phase Power MOSFET Controller

A3938

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

VBB. Motor power supply connection for the A3938 and

for power MOSFETs. It is good practice to connect a decou-

pling capacitor from this pin to AGND, as close to the device

pins as possible.

REF. Analog input to current limit comparator. Voltage

applied here sets the peak load current according to the fol-

lowing equation:

ITRIP = VREF / RSENSE

LCAP. 5 V reference to power internal logic and provide

low current for DEAD pin and FAULT pin. Connection for

0.1 μF external capacitor for decoupling.

DEAD. Analog input. A resistor between DEAD and LCAP

is selected to adjust turn-off time to turn-on time. This

delay is needed to prevent cross-conduction in the external

power MOSFETs. See the section Application Information

for details on setting dead time.

SENSE. Analog input to the current limit comparator.

Voltage representing load current appears on this pin. Voltage

transients that are seen at this pin when the drivers turn on

are ignored for period of time, tBLANK.

AGND. Analog reference ground.

PGND. Return for low-side gate drivers. This should be

connected to the PCB power ground.

H1 H2 H3 DIR GLA GLB GLC GHA GHB GHC SA SB SC

1011001100HI ZLO

1001001010 Z HILO

1101100010LOHIZ

0101100001LOZHI

0111010001 ZLOHI

0011010100HILOZ

1010100001LOZHI

1000010001 ZLOHI

1100010100HILOZ

0100001100HI ZLO

0110001010 Z HILO

0010100010LOHIZ

Commutation Truth Table

MODE PWM RESET Quadrant Mode of Operation**

0* 0 0 Fast decay PWM chop – current decay with opposite of selected low-

side drivers ON.

0* 1 0 Fast Decay Selected drivers ON. If current limiting, opposite of selected

low-side drivers ON.

1 0 0 Slow decay PWM chop – current decay with both low-side drivers ON.

1 1 0 Slow Decay Selected drivers ON. If current limiting, both low-side drivers ON.

XX 1 X

All high-side drivers OFF, low-sides see BRKSEL stored.

Clears storable faults.

* Low-side, only, Synchronous Rectiﬁ cation mode.

**See Commutation Truth Table for meaning of “both” and "selected."

Input Logic

Three-Phase Power MOSFET Controller

A3938

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Synchronous Rectiﬁ cation. To reduce power con-

sumption in the external MOSFETs, during the load current

recirculation PWM-off cycle, the A3938 control logic turns

on the appropriate low-side driver only. The reverse body

diode of the power MOSFET conducts only during the dead

time required at each PWM transition, as usual. However,

unlike full synchronous rectiﬁ cation, the opposite high-side

FET’s body diode (not the RDSON) will carry the re-circulat-

ing current, be self-extinguishing, and not force the motor to

reverse direction.

Dead Time. To prevent cross-conduction, it is required to

have a delay between a high-side or low-side turn-off, and

the next turn-on event. The potential for cross-conduction

occurs with synchronous rectiﬁ cation, direction changes,

PWM, or after a bootstrap capacitor charging cycle. This

dead-time is set via a resistor from the DEAD pin to LCAP

and can be varied from 100 ns to 5.5 μs.

For a nominal case, given:

• 25°C ambient temperature, and

• 5.6 kΩ < Rdead < 470 kΩ,

tdead (nom,ns) = 37 + [(11.9

×10-3)

(Rdead + 500)]

For predicting worst-case overvoltage and temperature

extremes, use the following equations:

tdead (min,ns) = 10 + [(6.55

×10-3)

(Rdead + 350)]

tdead (max,ns) = 63 + [(17.2

×10-3)

×(Rdead + 650)]

For nominal comparison with Idead currents, also at 25°C

ambient temperature:

Idead = (Vlcap – Vbe ) / (Rdead + Rint)

where Vlcap = 5 V, Vbe = 0.7 V, and Rint

= 500 Ω.

Rather than use Rdead values near 470 kΩ, set Vdead

= 0 V,

which activates an internal (Idead

= 10 μA) current source.

The choice of power MOSFET and external gate resistance

determines the selection of the dead-time resistor. The dead

time should be made long enough to cover the variation of

the MOSFET capacitance and gate resistor tolerances (both

external and internal to the A3938).

Decoupling. The internal reference VREG supplies

current for the gate drive circuit. As the gates are driven

high, they will require current from an external decoupling

capacitor to support the transients. This capacitor should be

placed as close as possible to the VREG pin. The value of the

capacitor should be at least 20 times larger than the bootstrap

capacitor. Additionally, a 1 nF (or larger) ceramic monolithic

capacitor should be connected between LCAP and AGND, as

close to the device pins as possible.

Protection Circuitry. The A3938 has several protection

features:

• Bootstrap Monitor. The bootstrap capacitor is charged

whenever a sink-side MOSFET is on, an Sx output goes low,

or load current recirculates. This happens constantly during

normal operation.

Note: The high side will not be allowed to turn on before the

charging has decayed to less than approximately 9 mA.

• Undervoltage. VREG supplies the low-side gate driver

and the bootstrap charge current. It is critical to ensure that

the voltages are at a proper level before enabling any of the

outputs. The undervoltage circuit is active during power-up

and signals a fault, and also coasts or brakes (depending

on the stored BRKSEL setting) the motor during that time

period, until VREG is greater than approximately 10 V. On

powering down, a fault is signaled and the motor is coasted

or braked, depending on the stored setting for BRKSEL.

• Hall Invalid. Illegal codes for the Hall sensor inputs (0,0,0

or 1,1,1) force a fault and coast the motor. Noisy Hall lines

may cause Hall code errors, and therefore faults. Additional

external pull-up loading and ﬁ ltering may be required in

some systems.

Hint: Use dividers to the VREG terminal, than to the LCAP

terminal, because the VREG terminal has more current

capability.

• Thermal Shutdown. Junction temperatures greater than

165C cause the A3938 to signal a fault and coast the motor.

• Motor Lead. The A3938 signals a fault if the motor lead

is shorted to ground. A short-to-ground is assumed after a

high- side is turned on and greater than 2 V is measured

between the drain (VBB) and source (Sx) of the high-side

power MOSFET. This fault is cleared at the beginning of

Application Information

Three-Phase Power MOSFET Controller

A3938

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

each commutation. If a stalled motor results from a fault, the

fault can only be cleared by toggling the RESET pin or by a

power-up sequence.

Current Regulation. Load current can be regulated by

an internal ﬁ xed off-time, PWM-control circuit. When the

outputs of the MOSFETs are turned on, current increases in

the motor winding until it reaches a value given by:

ITRIP = VREF / RSENSE

At the trip point, the sense comparator resets the source

enable latch, turning off the source driver. At this point, load

inductance causes the current to recirculate for the ﬁ xed off-

time period. The current path during recirculation is deter-

mined by the conﬁ guration of the MODE and SR input pins.

The ﬁ xed off-time is determined by an external resistor, RT,

and capacitor, CT, connected in parallel from the RC terminal

to AGND. The ﬁ xed off-time is approximated by:

tOFF = RT

tOFF should be in the range between 10 μs and 50 μs. Larger

values for tOFF could result in audible noise problems. For

proper circuit operation, 10 kΩ < RT < 500 kΩ.

Torque control can be implemented by varying the REF input

voltage as long as the PWM input stays high. If direct control

of the torque/current is desired by PWM input, a voltage can

be applied to the REF pin to set an absolute maximum cur-

rent limit.

PWM Blank. The capacitor CT also serves as the means

to set the BLANK time duration. At the end of a PWM

off-cycle, a high-side gate selected by the commutation logic

turns on. At this time, large current transients can occur dur-

ing the reverse recovery time, trr, of the intrinsic body diodes

of the power MOSFETs. To prevent false tripping of the

sense comparator, the BLANK function disables the com-

parator for a time period deﬁ ned by:

tBLANK = 1.9

CT / (1

10-3 – [2 / RT])

The user must ensure that CT is large enough to cover the

current spike duration.

Braking. The A3938 dynamically brakes the motor by

forcing all low-side power MOSFETs on, and all high-side

power MOSFETs off. This effectively short-circuits the

BEMF and brakes the motor. During braking, the load cur-

rent can be approximated by:

IBRAKEPEAK = VBEMF / RLOAD

As the current does not ﬂ ow through the sense resistor dur-

ing a dynamic brake, care should be taken to ensure that the

maximum ratings of the power MOSFETs are not exceeded.

Note: On its rising edge, a RESET setting of 1 overrides the

BRAKE input pin and latches the condition selected by the

BRKSEL pin.

Power Loss Brake. The BRKCAP and BRKSEL pins

provide a power-down braking option. A Power-Loss Brake

Trigger Event, which is either an undervoltage on VREG

or a RESET = 1 rising edge, is sensed by the A3938, which

then dynamically brakes or coasts (depending on the stored

BRKSEL setting) the motor. The reservoir capacitor on the

BRKCAP pin provides the positive voltage that forces the

low-side gates of the power MOSFETs high, keeping them

on, even after supply voltage is lost. A stored setting of BRK-

SEL = 1 brakes the motor, but a stored setting of BRKSEL = 0

coasts it. The combined effect of these settings is shown in the

table Brake Control.

BRAKE BRKSEL Before Power Loss Brake Trigger Event After Power Loss Brake Trigger Event

0 0 Normal run mode Coast mode – All gate drive outputs OFF

0 1 Normal run mode Brake mode – All low-side gate drivers ON

1 0 Brake mode – All low-side gate drivers ON Coast mode – All gate drive outputs OFF

1 1 Brake mode – All low-side gate drivers ON Brake mode – All low-side gate drivers ON

Brake Control

Three-Phase Power MOSFET Controller

A3938

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Terminal List

Name Description Number

PGND Low-Side Gate Drive Return 36

RESET Control Input 1

GLC Low-Side Gate Drive Output, Phase C 2

SC Motor Connection, Phase C 3

GHC High-Side Gate Drive Output, Phase C 6

CC Bootstrap Capacitor, Phase C 7

GLB Low-Side Gate Drive Output, Phase B 8

SB Motor Connection, Phase B 9

GHB High-Side Gate Drive Output, Phase B 10

CB Bootstrap Capacitor, Phase B 11

GLA Low-Side Gate Drive Output, Phase A 12

SA Motor Connection, Phase A 13

GHA High-Side Gate Drive Output, Phase A 14

CA Bootstrap Capacitor, Phase A 15

VREG Gate Drive Supply 16

LCAP 5 V Output 17

FAULT Diagnostic Output 19

MODE Control Input 20

VBB Load Supply 21

H1 Hall Control Input 22

H3 Hall Control Input 24

H2 Hall Control Input 25

DIR Control Input 26

BRAKE Control Input 27

BRKCAP Power Loss Brake Reservoir Capacitor 28

BRKSEL Control Input 29

PWM Control Input 30

RC Connection for Fixed Off-Time R and C 31

SENSE Sense Resistor 32

REF Current Limit Adjust 33

DEAD Dead Time Adjust 34

AGND Ground 35

N/C Not Connected 4, 5, 18,

23, 37, 38

Three-Phase Power MOSFET Controller

A3938

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

LD Package, 38-pin TSSOP

1.20 MAX

4º

6.00

1.60

SEATING

PLANE

0.50

C0.10

38X C

0.30

0.10 ±0.05

0.22 ±0.05

4.40 ±0.10 6.40 ±0.20

9.70 ±0.10

0.15 +0.06

–0.05

GAUGE PLANE

SEATING PLANE

ATerminal #1 mark area

All dimensions nominal, not for tooling use

(reference JEDEC MO-153 BD-1)

Dimensions in millimeters

BReference pad layout (reference IPC SOP50P640X110-38M)

All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary

to meet application process requirements and PCB layout tolerances

PCB Layout Reference View

0.50

0.25

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 de par tures from the detail spec i fi ca tions as may be required to per-

mit improvements in the per for mance, 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’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the

failure of that life support device or system, or to affect the safety or effectiveness of that device or system.

The in for ma tion in clud ed herein is believed to be ac cu rate and reliable. How ev er, Allegro MicroSystems, Inc. assumes no re spon si bil i ty for its use;

nor for any in fringe ment of patents or other rights of third parties which may result from its use.

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