DRV8850: DRV8850: VPROPI left open, any issue?

Hi Jitendra,

Questions:

1. Do you have the VPROPI pin floating?

2. Have you probed the INx, OUTx, SR, VCP and/or VCC pins to see if similar noise is found?

Hi Jitendra,

Pinging the thread for a response. If there is no reply by tomorrow, I will have to close the thread. A new one will need to be reopened. Thank you.

Hello Hector,

The vpropi pin is connected to ground through a resistor. It is TI's evaluation board.

I will check for noise on other pins.

Additionally, you may also try to analyze VPROPI without a motor (e.g. a resistor) or a different motor to see if the noise comes from that aspect of your setup.

Hi Jitendra,

Any updates here? Thank you.

Hi Jitendra,

Any updates from your end? Pinging the thread for an update.

I did what you suggested.

Actually, it is not noise. When I drive the motor at full speed, no PWM the signal on VPROPI pin is clean and proportional to current/load.

When there is PWM applied, the PWM signal is reflected on VPROPI pin. How to smoothen it. I want to read this value using ADC of cc3220.

Attached is the signal capture on VPROPI pin during PWM.

Hi Jitendra,

Let me see if I understand your reply correctly:

When you drive the motor at full speed without a PWM signal, the voltage on VPROPI pin is clean and proportional to current/load. Correct?

When there is a PWM applied, the PWM signal is reflected on VPROPI pin. How do we smoothen it, as I want to read this value using ADC of cc3220. Correct?

If I understood correctly, then we need to find out what causes the VPROPI voltage to behave with that noise:

Did you verify VPROPI in PWM signal test condition with a motor load? Did you verify VPROPI in PWM signal test condition without a motor load?

Does the noise come from the PWM signal, propagate through the predriver to the gate signals, and then to the motor load? We can determine this theory by probing wih a motor load the PWM signals, probing the gate signals and then probing those same signals without a motor load.

HI Jitendra,

For your question:

Do I need to add some kind of filter on motor output?

-> I do not have 100% certainty that the issue comes from the motor utilized. We need to verify by either changing the motor load to a resistive load, or if you can probe the PWM and gate signals without the motor loard.

Hi Jitendra,

Additionally, if the hardware cables and lab setup is clean and without cables being one above another can help with avoiding noise propagating across the board level.

Please, keep me updated on your next steps.

Hi Jitendra,

I am pinging this conversation to verify if any additional testing has been conducted.