Raspberry Pi Motor Controller L6203

The L6203 is a full bridge driver based on DMOS power transistors, and manufactured by the SGS-Thomson Corporation. This IC in the Multiwatt11 package is on the Gertboard, therefore I decided to have a look at it. The last time I saw something like this was in a power supply that controlled an industrial high-power motor.

Double-Diffused Metal–Oxide–Semiconductor (DMOS)

DMOS is a hardy technology employed in high power applications such as controlling electric motors in elevator lifts, and automotive applications. DMOS power transistors can take much punishment and they always continue operating. It has some great safety features that make it an ideal component for the experienced professional. For safety it has built-in thermal overload protection, which will choke the current to a lower level if the chip overheats, including total thermal shutdown at 150 °C.

Supply Voltage Vs

This IC will operate on an absolute maximum voltage of 52 V, and minimum 12 V. The manual recommends a typical value of 36 V. I suppose if you were building robots for the television program "Robot Wars", then something high-powered, as this would be ideal. One thing for sure though is that it will need many batteries!

If you are planning to use this with 6 V and 9 V power supply, then it is not enough, as the absolute minimum operating voltage is 12 V.

Heatsink

If you are planning on using this IC to its maximum capacity with a pulsed output current of 5 A then you will need to fit it to a good quality heatsink and perhaps even an active cooling system such as a fan to lengthen the useful operating life of the component.

Back EMF

Large inductive motors will generate significant back EMF and you will need to fit protection diodes to the terminals of the motor. In addition, a separate power supply for the inductive loads will be useful.

Logic Levels

All the input pins are CMOS and TTL compatible to allow for easy interfacing with microcontroller circuits.

Bootstrap Capacitors

Bootstrap capacitors at pin 4 and pin 8 ensure that the DMOS transistors receive the correct gate to source voltage of 10 V. Charge pumps within the circuit and external capacitors produce this voltage. The datasheet recommends the capacitor value to be 10 nF.

Configuration Pins

An internal circuit provides reference voltage; however, this is by-passed by fitting a 0.22 µF capacitor between pin 9 and ground.

Enable pin 11 controls both channels. This is set to logic 1 and tied to either 5 V or 3.3 V rail of the digital control system. The absolute maximum voltage is 7 V.

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