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DRV8302 Current Protection

Nick Zwahlen1
Prodigy 20 points
Other Parts Discussed in Thread: DRV8302

Hello Together,

I've got a question about the Motordriver DRV8302. Exactly about the current protection OCP.

At the OC_ADJ I set the voltage to 200mV. My FET's at the H-Bridge have a RDSon around 15mOhm(Datasheet).

Now should the Driver Protection shut down the FET, when the current trough the FET bigger than 13 Ampere is.

The Driver Protection shut down to early. When the current nearly at 4 Ampere is.

I have also a shunt resistor in my circuit. This 50mOhm shunt resistor shouldn't have any influence to the current Protection(Datasheet)

Is this really true? or have the shunt also an action to the OCP?

Also possible is a problem with switching my FET. I use the PSMN014-60LS and switch with 4kHz.

The reference voltage OC_ADJ switching also at the moment. The DRV8302 have an OC sensing response time of 1.5us.

After 1.5us the voltage OC_ADJ is a little bit floating. Maybe is this floating the reason for the protection.

I thank you for an Answer and I apologize for my average english.

Nick Zwahlen

  • 0
    TI__Prodigy 560 points

    Hi,Nick

     the RDSon is around 15mOhm only  with the condition that VGS = 10 V; ID = 10 A; Tj = 25 °C,if the MOSFET temperature go higher, or if the  VGS  is  lower than 10V, the Rdson will be higher than 15mOhm, and than the current will acturally lower than 13A, by the way, the 4A is the average current or the peak current?

  • 0 in reply to Brady Lin
    Prodigy 20 points

    hello Brady,

    the 4A is the peak current, meassure over the shunt.

    About the conditions, my IDrain shouldn't be higher than 12A and the Voltage is about 8 - 10V. The temp. is something about 50 -60° C.

    With a referencevoltage OC_ADJ 0.2V and a current 4A the RDSon have to be 50mOhm and that's to much.

    I allways get a PWM to the under FET (GL_B) and set the upper FET permanent ON.

    Yesterday I changed that, know is the under FET permanen ON and I pulse the upper FET with a PWM.

    The circuit works now faultless.

    I'm really not sure if it have something to do with the layout or something like that. The have an experiment Print.

    If you have any ideas I be interested.

    Thank you for the Post.

    kindly regards Nick