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DRV8323: sense OCP configuration block diagram and sense resistor usage

user021864
Intellectual 2145 points
Part Number: DRV8323
Other Parts Discussed in Thread: BOOSTXL-DRV8320S, DRV8320

Hi, 

1. My customer is having problem for the sense OCP configuration, can the sense resister be config like below capture in one of our reference design? 

Will there be any concern if only use one sense resistor for the over current protection? 

I just want to confirm this because our EVM is suggest to use 3 current resistor: 

Please let me know if there are concerns using only one sense resistor for OCP protection. 

2. Can you also provide the block diagram of the sense OCP? 

3. if only use the sense OCP protection but not using the current sense output result, can these pin left open? 

(VFRE, SOA, SOB, SOC, CAL)

Thank you.

  • 0
    TI__Guru** 114905 points

    Hi user021864,

    "1. My customer is having problem for the sense OCP configuration, can the sense resister be config like below capture in one of our reference design?

    Will there be any concern if only use one sense resistor for the over current protection?

    I just want to confirm this because our EVM is suggest to use 3 current resistor:

    Please let me know if there are concerns using only one sense resistor for OCP protection."

    The DRV8323 can be configured to operate with one, two or three sense resistors. The EVM is configured with three to allow FOC operation. Using one sense resistor implies trapezoidal operation.

    Please refer to the BOOSTXL-DRV8320S for an example of connections using a single sense resistor and external current sense amplifier.

    There is no concern about overcurrent protection. The sense resistor does not provide OCP protection. Overcurrent protection is provided by monitoring the Vds voltage of the FETs.

    "2. Can you also provide the block diagram of the sense OCP?"

    Please refer to section 8.3.1.4.4 of the datasheet (MOSFET Vds Monitors) for operational details of the monitors.

    "3. if only use the sense OCP protection but not using the current sense output result, can these pin left open?

    (VFRE, SOA, SOB, SOC, CAL)"

    Yes, these pins can be left open. If leaving these pins open, please consider using the DRV8320.

  • 0 in reply to Rick Duncan
    TI__Intellectual 2145 points

    Hi Rick, 

    Thanks for your feedback. 

    There is one question about sense OCP: 

    if there the current sense resistor doesn't provide the protection, why there are below description in the datasheet: 

    is the sense OCP same as the VDS OCP? 

    Thanks for your help.

  • 0 in reply to user021864
    TI__Guru** 114905 points

    Hi user021864,

    The sense OCP is not the same as the VDS OCP. The sense OCP has four setting, and the VDS OCP has 7 (HW device) or 16 (SPI device).

    The sense resistor is optional. It can be disabled by:

    1) not using the sense resistor,
    2) setting the OCP_MOD to 1xb in the SPI device, or
    3) setting the DIS_SEN bit to 1b in the SPI device

    If a sense resistor is used, the Vsen_ocp can provide a more accurate overcurrent measurement compared to the Vds of the FETs.