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DRV8912-Q1: Is there no issue by on resistance variation with half bridge parallel connection?

Part Number: DRV8912-Q1
Other Parts Discussed in Thread: DRV8906-Q1

Hi team, 

Is there no issue by on its resistance variation with half bridge parallel connection?

I would like to use a 3A peak motor load with some of other loads such as LED or additional motors.
DRV8912-Q1 datasheet says it could deal with 3A by operating multiple half bridge in parallel for current dividing. Then I am worried about on resistance variation. Is there any care points to use this operation to deal with high load motor by DRV8912-Q1?

Regards,
Ochi

  • Hi Ochi san,

    For 3A peak motor, DRV8912-Q1 parallel mode is good enough. Regarding resistor variation, it should not be issue. Each channel has 0.75ohm(High Side) and 0.75ohm(Low side) only. In parallel mode, can be 1/6 each. Even if resistance variation exists, should be OK for motor operation.

    regards

    Shinya 

  • Hi Shinya, 

    We would like to just 6 half bridge for 3A motor because there are other loads we want to use such as LEDs.
    In addition, motor needs forward and reverse current; there are just 3 parallel high side switches and other 3 parallel low side switches on motor current flow. Is it possible to deal with it by DRV8912-Q1 (or DRV8906-Q1) considering resistor variation?

    Regards,
    Ochi

  • Hi Ochi san

    To support 3A motor + others(LEDs), DRV8912-Q1 is better than DRV8906-Q1 for thermal view point. If you drive 3A contious with 3 H bridge, die temp may be too high under high Ta(e.g)85C.

    Then Customer can use 4-5 H bridge for 3A with parallel mode, then drive LEDs with remaining 2 half bridge.  

    regards

    Shinya Morita

  • Hi Morita-san, 

    Thank you. I understood there could be junction temp issue which may lead thermal shutdown.

    How about resistance variation? Do you have on resistance min and max value for all operating temperature range?
    In the case of 3 high side switches and 3 low side switches on 3A motor current path, do we have to care about current limit minimum value; 1.3A?  I am worried about one half bridge disabled due to OCP, then other 2 half bridge also goes disabled. 

    If R1=0.75 and R2=R2=1.5, then one half-bridge current exceeds its OCP minimum value. 

    DRV89xx_current dividing_E2E.xlsx

    Regards,
    Ochi

  • HI Ochi san

    I understand your concern. Your concern also support why DRV8912-Q1 is better to recommend.

    For resistance variation, main factor is temperature and part to part. Channel to channel variation is smaller than those conditions.

    regards

    Shinya Morita