3

Package Pin Description

PACKAGE PIN #

PIN SYMBOL

FUNCTION

16L PDIP

(internally fused leads)

1

DIR1

CMOS compatible input pin controls direction of current

through OUT1

2

C1

RC filter capacitor for OUT1 connected to Ground

3

IN1

CMOS compatible input pin controls output OUT1A and 1B

4,5,12,13

Gnd

Ground connection

6

OUT1A

One half of H-bridge output stage 1

7

VS1

Supply voltage

8

OUT1B

One half of H-bridge output stage 1

9

OUT2B

One half of H-bridge output stage 2

10

VS2

Supply voltage

11

OUT2A

One half of H-bridge output stage 2

14

IN2

CMOS compatible input pin controls output OUT2A and 2B

15

C2

RC filter capacitor for OUT2 connected to Ground

16

DIR2

CMOS compatible input pin controls direction of current

through OUT2

Each output stage contains 4 power NPN transistors

arranged in a traditional H bridge configuration. Current

flow through the two outputs (OUTxA, OUTxB) in each

H-bridge is controlled by the logic signal DIRx.

PWM input signals from the microprocessor, are filtered

on chip and sent to the output stage. The duty cycle of the

PWM signal is proportional to output voltage. The RC fil-

ter reduces the noise of the PWM input signal by slowing

its slew rate: i.e., the output signal is converted from a

square wave to an exponential sawtooth waveform. An

external capacitor (Cx) controls the slew rate for each H

bridge.

When the voltage on the control pin (INx) is low, both

halves of the H bridge are off (Table 1). When INx is high,

DIR controls the flow of current through the H-bridge. If

DIRx=0, current flows from OUTxA out to the coil and

back in through OUTxB. If DIRx=1, current flows from

OUTxB out to the coil and back in through OUTxA.

Table 1. Logic Control of H-Bridge

The high side driver transistor in each H-bridge is current

limited as a protection against a short circuit fault condi-

tion. If an over voltage or a thermal runaway fault condi-

tions occurs, all outputs shut down.

Output Stage

Motor Direction Control

Protection

Input

Direction

Outputs

INX

DIRX

OUTxA

OUTxB

0X

0

0

10

1

0

11

0

1

Circuit Description

Application Diagram

1

IN1

C1

Gnd

Gnd

OUT1B

VS1

DIR1

C2

Gnd

Gnd

OUT2A

VS2

DIR2

COIL1

COIL2

Air Core

Gauge

Circular

Speedometer

* 0.047

µF

OUT1A

OUT2B

IN2