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DRV8837: Parallel use

Fengyu Leng
Intellectual 970 points
Part Number: DRV8837
Other Parts Discussed in Thread: , DRV8212

Hi team,

Our customer wants a BDC driver with driver current greater than 3A. It's powered by 1S battery. Supply voltage is 3.5V-4.2V.

Due to the limitations of PCB, they used 2pcs DRV8837 and put them in parallel. That is, put two OUT1 pins of 2pcs DRV8837 together, And put  two OUT2 pins of 2pcs DRV8837 together. Then it diver the motor.

May I ask if there are some potential risks about  parallel use? And could you please give some suggestions?

Best regards,

Fengyu

  • 0
    TI__Guru 54695 points

    Fengyu,

    We can not recommend this.  Timing can be different between the 2 DRV8837 devices and cause a shoot thru event from power supply to GND.

    Can they use another device that was designed exactly for 1S battery operation and high current?

    https://www.ti.com/product/DRV8850

    Regards,

    Ryan

  • 0 in reply to Ryan Kehr
    TI__Intellectual 970 points

    Hi Ryan,

    Thanks for your reply. Our customers' EE is toothbrush. The space of PCB is limited. They have made their DRV8837EVM and plan to test.

    Here is their schematic. They use M_PWM1 to control both DRV8837. Will it still have the risk of shoot through? If so, what's the detailed reason?

    Besides, I also want to ask a question about DRV8212. I noticed that DRV8212 has  "parallel half-bridge mode" If driver current is still not enough, can we use DRV8212 in parallel just like current method DRV8837 using in the schematic.

    Best regards,

    Fengyu

  • +1 in reply to Fengyu Leng
    TI__Guru 54695 points

    Fengyu,

    Yes, you can parallel outputs of DRV8212 to drive one side of motor and use same idea to drive the other side of the motor.  This would be OK. 

    You just should not parallel connect two DIFFERENT DRVs.  Reason is the propagation delay from input to output can be different across two ICs.  So, one output may still be HIGH state while the parallel connected output can be in LOW state (not fully transitioned).  This causes a short-to-GND,

    Regards,

    Ryan

  • 0 in reply to Ryan Kehr
    TI__Intellectual 970 points

    Hi Ryan,

    Well - received. Thanks very much.

    Regards,

    Fengyu