DRV8702-Q1: Negative sense current

Federico Silva

Part Number: DRV8702-Q1

Hi,

I have a DRV8702 driving a full H-bridge via independent PWM. I want to use the sense resistor as a means to detect a short circuit. However, as the H--bridge and the resistor are in parallel to the bulk capacitor, the current seen by the resistor can be negative also (my load is pretty inductive).

From the datasheet I'm not certain what's the behaviour of the driver in such case. What happens when Vsp is negative? The tripping circuit acts also? It trips when Vsp< -1 V?

Thanks,

Federico

over 6 years ago

0 Hector Hernandez Luque over 6 years ago

TI__Expert 8985 points

Hi Federico,

I am looking into this point and I will get back to you.

0 Hector Hernandez Luque over 6 years ago in reply to Hector Hernandez Luque

TI__Expert 8985 points

Hi Federico,

The current regulation circuitry is not designed for negative voltage short circuit detection. If you look at the absolute maximum of SP (-0.5V) and SN (-0.3V), you will notice that any value below -0.2V in SP-SN can result in device damage.

We can review your schematic and understand what you are trying to achieve with y our sense resistor being placed in parallel to the bulk cap to suggest a better way to regulate your current.

Let me know if you wish to have a schematic review.

0 Federico Silva over 6 years ago in reply to Hector Hernandez Luque

Intellectual 795 points

Hi,

The schematic is pretty much the same as the evaluation board. Here is an image:

Regards,

Federico

0 Hector Hernandez Luque over 6 years ago in reply to Federico Silva

TI__Expert 8985 points

Hi Federico,

From the schematic, I notice that the sense resistor, RA, is not parallel to the bulk caps. you should not see negative voltage at -1 V as you are describing.

Can you verify that you are seeing this voltage on RA and if you are measuring the voltage in the correct layout location?

Can you provide a waveform of SP-SN = -1 V along with GH, SH, and GL?

0 Hector Hernandez Luque over 6 years ago in reply to Hector Hernandez Luque

TI__Expert 8985 points

Hi Federico,

Pinging this conversation to verify for any updates. Thank you.

0 Federico Silva over 6 years ago in reply to Hector Hernandez Luque

Intellectual 795 points

Hi,

Sorry for the delay. Here's a capture of the simulation (I do not have the board yet, I'l waiting to resolve this issue). Note that in here I used a 100mR resistor and V(n017) is the SP voltage.

Regards,

Federico

0 Hector Hernandez Luque over 6 years ago in reply to Federico Silva

TI__Expert 8985 points

Hi Federico,

Were you able to acquire a board?

There can be a component parameter or a circuit setup issue on your simulation. Have you verified the nodes and the component connections to see if they all match the EVM? Have you gone through the EVM's schematic or the datasheet's recommended component sections to see if the simulation has the component parameters designed as required? Thanks.

0 Hector Hernandez Luque over 6 years ago in reply to Hector Hernandez Luque

TI__Expert 8985 points

Hi Federico,

Pinging this conversation to see if there are any updates. Thank you.

0 Hector Hernandez Luque over 6 years ago in reply to Hector Hernandez Luque

TI__Expert 8985 points

Hi Federico,

We have not heard from you in some time, and are assuming your issue has been resolved. If it has not, please reply to this thread or if the thread is locked please select "Ask a related question" at the top right of the screen.

0 Federico Silva over 6 years ago in reply to Hector Hernandez Luque

Intellectual 795 points

Hi,

I'm sorry for the delay, I was on leave.

No, I wasn't able to acquire a board. Anyhow, I'll look into what you've told me.

Thanks for everything,
Federico

Motor drivers

Motor drivers forum

DRV8702-Q1: Negative sense current