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DRV8842 non-linear output problem

Matthijs Oonk
Prodigy 10 points
Other Parts Discussed in Thread: DRV8842

Were using the DRV8842 as a amplifier to drive a voice coil type actuator (2mH 8Ohms) with a 24V supply. The current regulation is disabled (Rsense = 0Ohm) and we use the DRV8842 as a voltage amplifier.

What we see is non-linear behavior from -3V to +3V.

This curve is different with every individual DRV8842 and can't be characterized. We have used multiple PWM modes and the result is always the same. A thing to notice is we see the PWM output edges jitter when the inputs (IN1,IN2) are stable microcontroller timer produced.

We expect the large dead-times or blanking times (dynamic) to be the problem. When i connect a H-bridge with a small dead time setting the output is linear around 0V.

Are we doing something wrong or is the linearity around 0V output just this unpredictable?

Thanks, Matthew

  • 0
    TI__Mastermind 26065 points
    Hi Motthew,

    I think if you do an open loop PWM control to regulate the current, the result cann't be accurate by many factors, such as the PWM jitter, coil parameters, dead time, decay parameters.

    One way possible is to use the on-device current regulation loop with sense resistor.
    Or add external current feedback circuit.

    Could show more detail on your schematic and inputs?

    Best regards,