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DRV8872: DRV8872 output jitter

Ivan Mitic21
Prodigy 140 points
Part Number: DRV8872
Other Parts Discussed in Thread: DRV8412, DRV8800, DRV8844

Hi,

I am using the DRV8872 to drive a voice coil (inductive load).

I have made a test with PWM running at frequency of 100kHz and D=50%. The VM was supplied with 12V and ISEN was shorted to GND.

I have observed a jitter in the output signal which caused further problems in my system. The jitter was caused by the non constant propagation delay in between input signal (both rising and falling edge) and output signal and was in between 700ns and 800ns (the whole pulse was jittering).

Is this a normal behaivour of the DRV8872?

  • 0
    TI__Guru 56650 points

    Ivan,

    DRV8872's input signal will synchronize with the internal clock and pass the output. So, the output jitter is about 200ns. It is normal.

    DRV8800/1; DRV8844 and DRV8412 or DRV8432 input signal don't need to synchronize with the internal clock. So, the jitter is about 20ns.

  • 0 in reply to Wang5577
    Prodigy 140 points

    Could you please recommend a driver which will allow me to achive sub ns resoultion?
    Are there any which are strictly analogue? (no clocks to cause jitter and reduce resolution)...

    Best regards,

    Ivan

  • 0 in reply to Ivan Mitic21
    TI__Guru 56650 points

    Ivan,

    DRV8412 and DRV8432 can support upto 500kHz. I would think the jitter may be less than DRV8800/01. But, I won't think it can achieve sub ns. I don't think we have a drive to achieve sub ns. From the input signal to output signal, the signal has to pass several analog gate and transistor. The jitter can be caused by the part by part variation due to gate threshold and gate capacitance variation.

  • 0 in reply to Wang5577
    Prodigy 140 points

    Hi,

    Can you please tell me if there is a difference in architecture in between DRV8412, DRV8432 and the DRV8872?

    I can not say from just looking at the datasheet block diagram, but it looks like that the DRV8412 directly drives the outputs (without sampling/syncrhronization) while the DRV8872 feeds everything to a "logic core" which syncrnogizes all incomming signals to its internal clock causing this jitter...

    Ivan

  • 0 in reply to Ivan Mitic21
    TI__Guru 56650 points

    Ivan,

    Datasheet doesn't give the gate drive detail from input to output.

    DRV8872's input signal will synchronize with the internal clock and pass the output. So, the output jitter is about 200ns. It is normal.

    DRV8800/1; DRV8844 and DRV8412 or DRV8432 input signal don't need to synchronize with the internal clock.

    The difference is due to the input noise filter design. DRV8872 uses the clock synchronization method to filter out the input glitch noise. DRV8412 doesn't use the clock synchronization method the filter out the input glitch noise.