DRV8701: DRV8701 Voff

Hi Mason,

Measure the SO pin when the DRV8701 is not driving current. This will be the same condition as the datasheet:

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
VOFF SO offset VSP = VSN = GND 50 250 mV

Thank you for your prompt response.
Is not change measured Voff value when the drv8701 is driving current?

I would like use external current limit circuit using SO pin. but voltage level's deviation is too big each ICs.
I know drv8701 has OCP function. but my customer want double protection for reliability.

Hi Mason,

Can you describe the deviation in more detail?

What level of accuracy is desired?
How do you plan to use the SO pin? Is there a schematic that will help me understand the concern?

Are you referring to the SO offset? The SO offset includes the amplifier gain.

Measured Voff value is 20~100mV when the drv8701 is not driving. is it normal?

MCU detects voltage on SO pin and control the drv8701.

Actually, it is same method with drv8701's OCP.

ICHOP= (VREF-VOFFSET)/ (RSENSE*Av)

But Voffset's deviation is 50mV~250mV.

How can drv8701 limit the current value exactly?

Hi Mason,

What value current are you trying to limit? What tolerance is acceptable?

Most motors do not need current limiting to be exact. There are tolerances throughout the system, such as VM, motor resistance and inductance, amplifier gain and offset, delays in firmware or hardware, and others that prevent accurate current limitation.