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DRV8881: Peak current and SOA

Yuto Sakai
Mastermind 6100 points
Part Number: DRV8881

Hi,

What is the peak current of DRV8881?
Or can you provide SOA data for internal FET?

Our customer are looking for a device that will not break when the output is short-circuited, and will have a protection operation.
This device has an OCP but OCP has a deglitching time of 2μs.
I would like to judge how much peak current can flow before OCP is applied.

Best regards,
Yuto Sakai

  • 0
    TI__Mastermind 37683 points

    Hi Yuto-san,

    The DRV8881 internal FETs could experience a current higher than the typical OCP trip value of 3.6A during a short circuit. However, the device will limit that current by disconnecting the gate driver. Basically, this increases the RDSon of the FET and the current through the FET will be limited to a level within the SOA of the FET. 

  • 0 in reply to Pablo Armet
    Mastermind 6100 points

    Hi,

    Thank you for your reply.
    I believe that the operation that limits the current by disconnecting the gate driver is OCP operation.
    Also, I think that the operation will start 2μs after exceeding the trip value (typ 3.6A).

    I think that the current exceeding the trip value flows through the FET until OCP is activated.
    I would like to judge if there is a SOA problem with the internal FET for 2 μs before OCP is activated.
    Could you tell me the SOA data of FET or the reference value of peak current?

    Best regards,
    Yuto Sakai

  • 0 in reply to Yuto Sakai
    TI__Mastermind 37683 points

    Hi,

    Section 2 of "Understanding Motor Driver Current Ratings" application report, http://www.ti.com/lit/an/slva505/slva505.pdf, does a good job at explaining how the motor driver OCP operation functions.

    The OCP operation in the DRV8881 is similar to the one explained in the app report. As soon as the current spikes up, the current through the FETs will be limited by a fast-acting analog current limiting circuit (usually around nanoseconds) and brought down to a safe level for the remainder of the 2us deglitch time as shown in the scope shot below. The current limiting circuit will ensure that there are no high current related SOA problems with the internal FETs for the 2us before OCP is activated.

    Please read the app report to learn more.