DRV8881: DRV8881P current sense resistors

Part Number: DRV8881

Hi,

I am working on schematic layout of DRV8881 on Altium and I have two questions:

I was wondering what value of current sense resistor should I use and how can I find footprint for sense resistor at Altium? (Pin AISEN and BISEN are connected to sense resistor )

Also, do I have to connect any resistor between pins AVREF and BVREF and V3P3?

Thanks!!

Regards,

Farinaz 

Hi Farinaz,

The value of the resistor is based on equation (1) of the datasheet, plus the absolute maximum voltage allowed on the xISEN pins of +/-0.55V.

What do you mean "how can I find footprin for sense resistor at Altium"?

You can connect AVREF and BVREF directly to V3P3 as long as the Itrip current * sense resistor does not violate the absolute maximum voltage of the xISEN pins. Typically as the current increases, lower the resistance is preferred to reduce the power through the resistor.

Hi Rick,

Thank you so much for the reply and your help!

From this equation, I should calculate the value of resistor I need to use for my circuit:

From the DRV881 evaluation module, current sense resistor seems larger than normal resistor. And by footprint of resistor I meant to ask, can I use normal resistor as long as the value is correct based on equation (1)? I am working of schematic of the board and I am using motor driver DRV8881. 

For AVREF and BVREF, they should connect to resistor as well and the value of the resistor should not violate the absolute maximum voltage of the xISEN pins?

Thanks again!!

Regards,

Farinaz

Thank you so much Rick!!