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DRV8711: OCP

Shota Mago
Expert 8110 points
Part Number: DRV8711
Other Parts Discussed in Thread: , CSD18531Q5A, DRV8886

Hi team,

My customer considers to use DRV8711 and he provided a question in terms of OCP threshold.

According to "DRV8711 Quick Spin and Tuning Guide", target over current protection level can be calculated by I_OCP = OCPTH / R_DS(ON) and Table 1(DRV8711EVM configuration) shows that I_OCP is set to 2A.

However, Ron of CSD18531Q5A is at most 5.8mΩ and even if we set OCPTH=250mV , I_OCP can be derived as 250mV/5.8mΩ=43A.

How can we derive 2A from  I_OCP = OCPTH / R_DS(ON)?

Also, is OCP nothing to do with R_SENSE value?

I'm looking forward to hearing back from you.

Best regards,

Shota Mago

  • 0
    TI__Mastermind 37683 points

    Hello Shota,

    "Also, is OCP nothing to do with R_SENSE value?"

    [Answer] Rsense is used for current regulation which is different from OCP

    "How can we derive 2A from  I_OCP = OCPTH / R_DS(ON)?"

    [Answer] A way to bring the I_OCP dowm to 2A is to select a FET with higher R_DS(ON). However, if you are planning on regulating the current at 2A, then you can just adjust the Rsense resistors.  

                   If you cannot use a higher R_DS(ON) FET on your design and need an OCP current threshold to be ~2A, then you can take a look at the DRV8886 as an alternative part. The DRV8886 has the following specs:

    • Vin: 8V - 37V
    • 2-A Full-Scale per bridge
    • 3-A Peak per bridge
    • Up to 1/16 microstep.
    • Integrated H-bridge
    • I_OCP=3A TYP