2961 View Datasheet(PDF) - Allegro MicroSystems

Part Name

Description

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2961

HIGH-CURRENT HALF-BRIDGE PRINTHEAD/MOTOR DRIVER—WITH INTERNAL CURRENT SENSING AND CONTROL

Allegro MicroSystems 

2961

HIGH-CURRENT

HALF-BRIDGE

PRINTHEAD/MOTOR DRIVER

The load supply (VBB) should be well decoupled with a capacitor

placed as close as possible to the device.

The EMITTER pin should be connected to a high-current power

ground.

Thermal shutdown protection circuitry is activated and turns OFF

both output drivers at a junction temperature of typically +165°C. It is

intended only to protect the device from catastrophic failures due to

excessive junction temperatures and should not imply that output short

circuits are permitted. The output drivers are re-enabled when the

junction temperature cools down to approximately +145°C.

MOTOR DRIVER APPLICATIONS

Two UDN2961B/Ws can be cross connected as shown to form a

full-bridge driver circuit. Two full-bridge circuits are needed to drive a

two-phase bipolar stepper motor. When in a full-bridge configuration,

one INPUT signal must be logically inverted from the other INPUT

signal to prevent the simultaneous conduction of a source driver from

one half-bridge and the sink driver from the other half-bridge. In order

to prevent crossover currents, a turn-ON delay time of 3 µs is needed

between the time an INPUT signal for one of the half bridges goes high

and the INPUT signal for the other half bridge goes low.

In addition to the two external ground clamp diodes, diodes in

series with the load to the SINK OUT are needed in a full-bridge

configuration. These series diodes prevent the sink drivers from

conducting on the inverse mode, which can occur when the opposite

half-bridge ground clamp diode is conducting and forces the sink driver

collector below ground.

If fast current decay is used (MODE = logic high) or pulse width

modulation of the load-current direction is used, diodes in series with

the load to the SOURCE OUT are needed. These series diodes

prevent the SOURCE OUT from inverse conducting during the recircu-

lation period and thereby prevent shoot-through currents from occuring

as the drivers turn back ON.

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

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