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Bidirectional Current Buffer

The L293 and L293D are quadruple high-current half-H drivers. The L293 is designed to provide bidirectional drive currents of up to 1 A at voltages from 4.5 V to 36 V. The L293D is designed to provide bidirectional drive currents of up to 600-mA at voltages from 4.5 V to 36 V. All inputs are TTL compatible. Each output is a complete totem-pole drive circuit, with a Darlington transistor sink and a pseudo-Darlington source.

WHERE TO USE?

The most common use of bidirectional current buffers is to drive a motor in both directions. Both devices are also used to drive inductive loads such as relays, solenoids, dc and bipolar stepping motors, as well as other high-current/high-voltage loads in positive supply applications.

HOW TO USE?

Drivers are enabled in pairs, with drivers 1 and 2 enabled by 1,2EN and drivers 3 and 4 enabled by 3,4EN. When an enable input is high, the associated drivers are enabled and their outputs are active & in phase with their inputs. When the enable input is low, those drivers are disabled, and their outputs are off and in the high-impedance state.

This one bidirectional current buffer IC can be used to drive 2 motors simultaneously as shown:

HOW IT WORKS?

Now the working of the both motors is controlled by the inputs 1A, 2A, 3A, 4A & 1,2EN & 3,4 EN and the inputs can be controlled using micro-controller or using switches etc. The following tables illustrate the working of both motors according to the inputs:

1A2A1,2EN1Y2YMOTOR1
XX0ZZSTOP
10110RUNS CLOCKWISE
01101RUNS ANTI-CLOCK
00100STOP
11111STOP
3A4A3,4EN3Y4YMOTOR2
XX0ZZSTOP
10110RUNS CLOCKWISE
01101RUNS ANTI-CLOCK
00100STOP
11111STOP