TIDM-1000: Gain adjustment in CCS

Hi Rakesh,

Please make sure ADC inputs are max 3.3V tolerant. 

I think you are asking for ACQPS value adjustment. Please refer this App note: https://www.ti.com/lit/an/spracp5/spracp5.pdf?ts=1692123670285&ref_url=https%253A%252F%252Fwww.google.com%252F

Best,

Uttam Reddy Pailla

Hi Uttam,

Yes, we are keeping the same values as the evaluation board and it should not cross the 3.3V. Only difference is using AMC1311 instead of AMC1301. we adjusted the gain at the opamp using 62k instead of the 7.5k . so we should be around the same value as the evaluation board. But I can see that at 84V DC link I am getting 116V at the CCS. Can I adjust the scaling factor in c-code and get the same value as the measurement. 

The current sense is also different we are using a different current sensor as it need to measure higher current. In vienna.h file I can see VIENNA_iL1MeasOffset_pu. whether it need to be changed or somewhere else in the c-code. 

Thanks in advance.

Regards

Rakesh

Hi Rakesh,

This seems a very large difference from 84V to 116V.

1. When you probe at the output of op-amp what is the voltage you are seeing into the C2000? vs expected

2. What is the reference voltage set in your case i.e., external 3V/3.3V (or) internal 2.5V/3.3V?

3. Can you share a snipshot of the circuitry for AMC1311+op amp until it goes to C2000?

4. Last option should be adjusting the offset. 

best Regards,

Uttam

Hi Uttam,

Here is the snipshot from the schematic

We measured 301mV towards the C2000 at 100V dc link voltage. 

Where can we adjust the offset for the current measurement and voltage measurement. 

Regards

Rakesh

Hi Rakesh,

Considering gain values from the below circuit it should show 600mV. I am not sure how you are getting 301mV. Can you please verify again.

By backtracing the signal from output to input i.e., with 301mV output instead of 91mV should see 45.6mV input ??

I am unclear on why such a drop is seen. I have looked into AMC1311 (9.2.2) it looks good to me. I wouldnt change the VIENNA_iL1MeasOffset_pu = 0 unless required as it messes the control this can be modified in vienna.C.

I will reassign this query to AMC1311 experts to have their feedback on this. 

Thanks & Regards,

Uttam

Hi Uttam, 

yes the voltage between the dc+ and midpoint is only 50V then it’s 301mV.

we are able to get the correct value now , without adjusting the offset. Thanks. 

Currently experiencing with difficulty with control loop stability using SFRA. Is there any material available.

Regards

Rakesh