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Original question:

DRV2510-Q1: Need for snubbing back emf?

DRV2510-Q1: Back EMF current path

Mochi
Genius 4165 points
Part Number: DRV2510-Q1

Hello,

Our customer is investigating DRV2510Q1 or DRV2511Q1 for solenoid haptics driver.

Back EMF current is generated when turn off the power supply.

We understood, in this case internal Diode will activate to bypath the revers current as original E2E thread mentioned.

Here is question, what is Voltage and Current rating of this internal diode?

Can we expect it is same of half bridge FET specification because the diode is worked during PWM output to inductor load?  

Regards,

Mochizuki

  • 0
    TI__Mastermind 46835 points

    Hi Mochizuki-san,

    Based on the previous E2E thread, I agree that 40V is probably the voltage limit of the diodes. You can expect the datasheet specs of the output FETs to at least match the Back EMF diodes, but I don't know for certain what the true limit is. We can try to look around internally.

    Best regards,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    TI__Mastermind 46835 points

    Hi Mochizuki-san,

    Because this use case falls out of the spec of the device it's hard to find the limit of these diodes. However it's probably a fair assumption that the diodes are at least as capable as the datasheet specs (current and voltage limit). The diodes are part of the body of the FET so they aren't working while the device is under load, but they are designed with that in mind since the output stage can be disabled at any time. The Midpower audio team recently did experiments on this exact phenomenon and found that reducing the size of the bulk caps can help limit the amount of back EMF current that is seen. If the amount of current becomes a concern that is what the customer can do to help mitigate it. You can also add resistance to the output line, but that is less desirable.

    Best regards,
    Jeff McPherson

  • 0 in reply to Jeff McPherson
    Genius 4165 points

    Hi Jeff, 

    Thank you for the elaboration.

    We understood this characteristics is outside of datasheet specification.

    But the customer can expect almost same spec. and external Shockey diode might be workaround if there is concern.

    Regards,

    Mochizuki