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TIDA-01629: Circuit issue

Part Number: TIDA-01629
Other Parts Discussed in Thread: DRV8350R

Hi team,

Here's an issue from the customer may need your help:

In the following schematic, what is the purpose of the two circuits highlighted with a red box? 

Could you help check this case? Thanks.

Best Regards,

Cherry

  • Hi Cherry,

    Thank you for your interest in the TIDSA-01629 and checking with us. the series RC filter is a snubber network, to reduce the transient over-and under-shoot of the switched node voltage vs. the power GND. The snubber network depends on the power FETs reverse recovery change, the turn-on and off time power FETs, DC-link and load current. It requires individual optimization and may not be needed depending on the system configuration. Please refer to Design guide — TIDA-01629, section 2.2.1.4 Power Stage System Considerations. 

    Please let me know when we can help with further questions. 

    Thanks. 

    Regards,
    Martin 

  • Hi Martin,

    Thanks for your support.

    What are the RC circuits in the upper and lower boxes? Is the following set low-pass filtering? So what about the upper box? 

    Thanks and regards,

    Cherry

  • Hi Cherry, 

    the RC circuits are the snubber network as described in my earlier post above.

    The snubber circuit is both boxes you marked, one series RC connects to GND (to minimize transient voltage undershoot), the other RC circuit interfaces to VIN to minimize transient voltage over-shoot.   

    With these snubbers we ensure switch node voltage of the DRV8350R (pins SHA, SHB and SHC) remain within the DRV8350R device specification, per 
    DRV8350R data sheet (SLVSDY6A –AUGUST 2018–REVISED JUNE 2019 ) section 7.1: Transient 200-ns high-side source sense pin voltage (SHx): –10 V (abs. MIN) VDRAIN + 10 V (abs. MAX). Please always check for latest data sheet. 

    As mentioned above, the snubber network depends on the power FETs reverse recovery change, the turn-on and off time power FETs, DC-link and load current. It requires individual optimization and may not be needed depending on the system configuration. Please refer to Design guide — TIDA-01629, section 2.2.1.4 Power Stage System Considerations. 

    Regards,
    Martin