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I have seen and understood the purpose of charge pumps. Used for pumping voltage levels in case of RS232 transceiver IC's. But most of the motor driver IC's also includes a internal charge pump circuitry. What is the exact purpose of this? As voltage required for the motor is already been given through external source.

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    \$\begingroup\$ Impossible to say generally. But perhaps to drive the H-bridge transistors? \$\endgroup\$ – Dzarda Apr 14 '15 at 9:33
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You have to drive the gate of the N-channel Power FET in the driver chip high enough to make the FET switch fully on. Since the chip is using N-Channel MOS-FETs in the high side of the H-Bridge, you have to provide a voltage higher than the motor source to make the gate switch on. The chips include a charge pump to generate the needed voltage so that you don't have to implement it separately.

See also this question.

This isn't a very good answer, but should provide enough key words for you to find more information on your own - and maybe one of the resident experts will provide a more detailed answer later on.

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