A3909 データシートの表示（PDF） - Allegro MicroSystems

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A3909

Dual Full Bridge Motor Driver

Allegro MicroSystems 

A3909

Dual Full Bridge Motor Driver

Functional Description

Device Operation

The 3909 is designed to operate two DC motors or a single

stepper motor. The outputs are PMOS source drivers combined

with low RDS(on) DMOS sink drivers.

Protection circuitry includes internal thermal shutdown, protec-

tion against shorted loads, and against outputs shorted to GND

or supply. Undervoltage lockout prevents damage by keeping the

outputs off until the driver has enough voltage to operate nor-

mally.

A low power standby (Sleep) mode is activated when all inputs

are low for longer than 1 ms. Sleep mode disables all of the cir-

cuitry making the IC ideal for battery operated applications.

Overcurrent Protection (OCP)

The A3909 is protected against accidental shorts or motor outputs

to ground and supply, as well as a shorted load condition. For

the source drivers, the current is monitored after the MOSFET is

turned on. If the current exceeds 1.8 A for longer than 2 μs, then

a fault condition is asserted. The sink driver utilizes a drain-to-

source voltage monitor. If the voltage exceeds 2 V for longer than

2 μs, the fault condition is asserted.

When a fault occurs, the IC immediately disables both sides of

the full bridge where the fault occurred. The full bridge input

commands will be ignored for a 2 ms period before being allowed

to retry. Each channel has independent overcurrent protection.

During OCP events, the absolute ratings may be exceeded for a

short period of time before the outputs are disabled.

Thermal Shutdown

If the die temperature increases to TJTSD , then all outputs are dis-

abled until the internal temperature falls below a hysteresis level,

TTSDHYS, of 20°C. Internal UVLO is detected on VBB to prevent

output drivers from turning on when below the UVLO threshold.

IN1

IN2

OUT1

OUT2

Current (12)

DC Motor Timing Diagram

tSTANDBY

2

3

4

5

6

7

1) Low power standby (Sleep) mode (IBB = 0)

2) On, reverse – 100% duty cycle

3) On, forward – 100% duty cycle

4) Slow decay PWM

5) Fast decay PWM

6) Coast

7) Low power standby (Sleep) mode

after tSTANBY (IBB = 0)

Allegro MicroSystems, LLC

5

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

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