DRV8353: Measure 1mA using the embedded DRV8353's amp in combination with INA ?

Emanuel Soares

Part Number: DRV8353
Other Parts Discussed in Thread: INA240

Hi,
I would like to acheive a 1mA precision combining the amp. inside the DRV8353 and another current amp. out of the IC. A possible solution would be using any suitable INA, which I would like to determine, based on the schematic below:

Note that the inline shunt is measured with, say, a INA240 cascaded with the internal amplifier in the DRV.
Whith this configuration, my goal is to achieve:
- Less or equal than 1mA resolution in current measurement;
- Bandwidth > 200kHz;

Considering a 1mOhm shunt resistor, I would like to ask:
1. In order to choose a suitable INAxxx, what should I take into account?
2. Is it possible to achieve considering the offset input of the INA240?
3. Also, is the summative contribution of noise being amplified from INA into the embedded amplifier relevant? How does it impact in the signal SNR?

Best Regards,
Emanuel

over 3 years ago

0 Akshay Rajeev Menon over 3 years ago

TI__Mastermind 24411 points

Hey Emanuel,

I will aim to provide feedback next week, but it might be delayed due to upcoming holidays.

Best,

Akshay

0 Emanuel Soares over 3 years ago in reply to Akshay Rajeev Menon

Intellectual 540 points

Hi, Akshay.

ok, no problem. I am waiting for your support.

Regards,
Emanuel

0 Akshay Rajeev Menon over 3 years ago in reply to Emanuel Soares

TI__Mastermind 24411 points

Hey Emanuel,

Thank you for your patience.

Best,

Akshay

0 Emanuel Soares over 2 years ago in reply to Akshay Rajeev Menon

Intellectual 540 points

Hi, Akshay,

Just remembering you to give me a feedback about the question above.

Regards,
Emanuel

0 Akshay Rajeev Menon over 2 years ago in reply to Emanuel Soares

TI__Mastermind 24411 points

Hey Emanuel,

Thank you for your patience.

What sort of voltage and current is expected at SPx?

Best,

Akshay

0 Emanuel Soares over 2 years ago in reply to Akshay Rajeev Menon

Intellectual 540 points

Vcc max.: 60v
max current on shunt: 100A

I need a precision of 1mA measurement.

Regards,
Emanuel

0 Akshay Rajeev Menon over 2 years ago in reply to Emanuel Soares

TI__Mastermind 24411 points

Hey Emanuel,

I discussed the issue with my team and we do not recommend cascading the external CSA with our driver's internal CSA. Since the SPX path is working as the sink for the low side FET and we don't want any interference there.

We recommend using the internal CSA for the larger overcurrent sensing and having a separate external in line phase current sense for the high precision current monitoring.

For more support on implementing in line current sense I suggest reaching out to the current sensing team's E2E forum.

Best,

Akshay

0 Emanuel Soares over 2 years ago in reply to Akshay Rajeev Menon

Intellectual 540 points

Hello, Akshay.

Akshay Rajeev Menon said:
SPX path is working as the sink for the low side FET and we don't want any interference there.

Can you clearify the question, I did not get the point when it comes to a problem on cascading the external CSA with the internal CSA from the DRV8353.

What you meant by SPX be working as the sink for the low side FET? And what kind of interference comes into play?

Regards,
Emanuel

0 Akshay Rajeev Menon over 2 years ago in reply to Emanuel Soares

TI__Mastermind 24411 points

Hey Emanuel,

The SPx is tied directly to the low side FET so when the LS FET needs to be turned on then SP is expected to be low but now the external CSA would supply voltage to SP pin and cause it to not be low. The team also mentioned that there might be issues with VDS monitoring on LS FET by having external CSA connected to it.

Cascading the two CSA’s is not a recommended approach from our driver’s standpoint. We suggest using the internal CSA for fault purposes and overcurrent and using the external inline current sense amplifier for the more precise measurements.

Hope this offers some clarification.

Best,

Akshay

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DRV8353: Measure 1mA using the embedded DRV8353's amp in combination with INA ?