hi,
can anyone please explain in brief the working of l293d.please refer to the attachment.i tried to understand the block diagram but i failed.please help
thank you.

 

Hi,
The SGS Thompson L293D is a dual half-bridge circuit, or it can be called a full bridge power device. This chip takes the logic signals meant to drive a motor, solenoid, or whatever else you want to connect to it across the bridge outputs, and allow a load current up to 600mA at up to a 36VDC power supply input. Note that the load connects across the left center connection to the right center connection, so that if the upper left and lower right switches are on, the load will have the input supply voltage positive on the left side and the return or ground on the right side. If the logic inputs are changed such that the lower left and upper right switches are on, then the load is connected in reverse polarity compared to the previous case. This allows a load to have a true AC drive without having to have an AC or dual power supply. However, this is a switching device. In order to control the load current, like motor speed, etc, the width of the pulses are modulated by the controller at a constant frequency, or there may be a constant width with a variable frequency to control the load more finely than just on or off.
In this case, it is a fairly low-frequency unit with a maximum drive speed of 5KHz.

Regards,
Kamran Kazem