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DRV8701: issue with SN SP when driver is in brake mode

jerem tolliug
Prodigy 90 points
Part Number: DRV8701

Hello

We are observing a weird issue on our last batch of board using a DRV8701. When the driver enter in brake mode to limit current, the GND seems very noisy and an ADC component on the board fails to acquire proper values.

Some boards works well some not at all.

We tried to measure the noise and some spikes about +/-2V appears on GND and VCC. However if we put the probe on a single pin one RSENSE terminals then all is OK. The DRV8701EVM board as a 1000pF between SP and SN which is not mentioned in the DRV8701 data sheet. Could it be related?

Our probe is a P2220 from Tektronix. If we change the attenuation from 1X to 10X then it fails again.

Probe characteristics seems to be

1X: 1MOhm  95pF in theory . (measured at 80 pF in practice)

10X: 10MOhm 16pF (measured at 18pF in practice)

There's no need for the probe to be connected to DSO, just GND and the probe so I assume this is something related with the RC characteristics of the probe.

Any tips to troubleshoots this issue?

  • 0
    TI__Guru 56650 points

    Jerem,

    "an ADC component  fails to acquire proper values". What ADC? Do you mean an ADC component measuring the voltage between SP and SN?

    "We tried to measure the noise and some spikes about +/-2V appears on GND and VCC. However if we put the probe on a single pin one RSENSE terminals then all is OK" It sounds like a layout issue. Where do you put the probe's ground? Does any current flow between probe's ground point and RSENSE terminals?

  • 0 in reply to Wang5577
    TI__Guru 56650 points

    Jerem,

    Let me temporarily close this post. You can reopen it by posting your answer here.