4

I am using L293d motor driver to drive 2 motors simutaniusly in several direction.

But I am not shure why there is 2 Vcc and 4 GND in this IC.

Can anyone tell explain it?

Thank You...

5

It's explain in the datasheet.

A VCC1 terminal, separate from VCC2, is provided for the logic inputs to minimize device power dissipation. (pg. 2)

VCC1 is for the logic and VCC2 is for the motor supply.

The four grounds are all tied together internally and act as a heatsink for the chip. (pg. 11)

2

Apart from heatsinking the four pins in parallel reduce the impedance (resistance) to ground. The actual bond wires that run from the chip to the leadframe are pretty thin and as an effect the resistance is relatively high. By wiring these pins in parallel the impedance is reduced which is a good and important property when you are trying to drive high current loads.

Also the ground potential on the chip will be slightly lifted proportonal to the current in the ground connections. In practice this may cause strange effects like logic levels shifting up and down with load current.

Best to attach GND all to the ground plane, the impedance on the PCB will be low and and the large copper surface helps to keep temperature down.

Vcc1 is for logic and will often interface with your 5V microcontroller. Vcc2 is the supply rail that will actually power the load.

2

They are connected together and used for heatsinking,

VS - is voltage supply

VSS - is logic level definition, if your uC logic level is 5V then power this with 5V. This will define voltage levels for the signal to be considered 0 or 1

1
  • Welcome to Arduino SE! Can you please explain a little more about the two pins? Not all new users know what logic level definition is... Jun 26 '14 at 20:39

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