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Original question:

BOOST-DRV8711: Current Measuring

What The Shunt Resistors Used in The DRV8711 do?

Hamdy Elasawy
Prodigy 145 points
Part Number: BOOST-DRV8711
Other Parts Discussed in Thread: DRV8711

Greatings, 

I wanted to take the current measurement from both shunt resistors in the DRV8711 Booster , but it seems that the booster isn't allowing that.

i asked previous Question here whether the DRV8711-BOOST Uses those shunt resistors to make a FEEDBACK Current loop, but the answer was no.

So What is the Application of the Two Sens Resistor on Board.

  • 0
    TI__Guru** 114905 points

    Hi Hamdy,

    Please refer to section 7.2 Functional Block Diagram and Figure 8 of the datasheet.

    In both you can see the sense resistor voltage is amplified and compared to a internal voltage. This voltage is used to regulate the current when used in stepper mode. The voltage can also be used to regulate the current in pwm mode when a brushed motor is starting.

    If you are operating in stepper mode, attempting to measure the current across the resistors is not possible. This is because the device is switching between PWM on and off using the internal current regulation engine.

    If you are operating in pwm mode and controlling the inputs directly without current regulation, it is possible to measure the current across the sense resistors. In this case you would take the current measurement toward the end of the PWM drive on cycle.

  • 0 in reply to Rick Duncan
    Prodigy 145 points

    Thank You Rick, this is all i need to know.