DRV8801: VPROPI driven low problem

Hi Gene,

Yes, overcurrent will cause VPROPI to read 0V. VPROPI is designed to read the current through the resistor to GND.

During an overcurrent event the current flows the opposite direction, causing the voltage to be negative. VPROPI cannot create a negative voltage.

Could you explain more detail about why during the overcurrent event the current flows the opposite direction?

Is it any relationship with sense trip voltage VTRIP= 0.5V?  when SENSE voltage is above 0.5V, then VPROPI is driven low to 0V. Is it a result or cause?

At this case, which operation mode ( decay) is it for over current? 

Thank you for your time

Best Regards

Gene

Hi Gene,

"Could you explain more detail about why during the overcurrent event the current flows the opposite direction?"

The current through the inductor does not flow in the opposite direction. The current through the resistor flows in the opposite direction.

Please refer to Figure 9 of the datasheet. During normal operation current flows as described by (1), Drive Current. When the voltage across the resistor reaches Vtrip, the outputs are disabled causing the current to flow in the direction shown by (2). The difference is the current flows through the body diodes.

"Is it any relationship with sense trip voltage VTRIP= 0.5V? when SENSE voltage is above 0.5V, then VPROPI is driven low to 0V. Is it a result or cause?"

VPROPI =0 when SENSE voltage is above 0.5V is a result.

"At this case, which operation mode ( decay) is it for over current? "

It is asynchronous fast decay. This means the FETs are disabled and the current flows through the body diodes of the FETs.

Hi Rick,
For the on-board charger application, what is the recommended operation mode when using DRV8801 for locking the charging gun? what is the consideration?
In the low side slow decay mode, does overcurrent still brings the VPROPI to 0?

Much appreciated
Gene

Hi Gene,

Most applications will use Mode1 = 1, Mode2 =0 (Low-side Slow Decay). This will minimize the current ripple in the motor when PWM'ing the outputs.

During slow decay (low side or high side), VPROPI measures 0 V. This is because the current is recirculating through the FETs.

Hi Rick,

Great. Thank you for updating me - very useful !

Gene