PGA400-Q1: Regardless of the capacitance value, the ADC calibration results are the same.

Downey Kim

Expert 2675 points

Part Number: PGA400-Q1

Hi TI team,

My customer made a PCB with the same circuit as the TIDA-00985.

http://www.ti.com/lit/ug/tidubn2a/tidubn2a.pdf

we have completed Section 9.4 of the linked document. we did try Section 9.5 while changing the capacitor value.

At 15pF, 20pF and 25pF, the same value is output.

Please guide what is wrong.

Fullscreen ADC_15p.txt Download

Fullscreen ADC_20p.txt Download

over 5 years ago

0 Scott Cummins over 5 years ago

TI__Mastermind 31655 points

Hello Downey,

Has the customer programmed any firmware into the OTP of the PGA400 before beginning the calibration?

Thanks,

0 Downey Kim over 5 years ago in reply to Scott Cummins

Expert 2675 points

Hi Scott,

Yes, they programmed the firmware for OTP to work.

We confirmed that EEPROM writing was done using OTP.

Thanks,

0 Scott Cummins over 5 years ago in reply to Downey Kim

TI__Mastermind 31655 points

Hi Downey,

Sorry for the delayed response. I'm bringing this to the attention of the engineer who built the reference design to further assist you.

Regards,

0 Downey Kim over 5 years ago in reply to Scott Cummins

Expert 2675 points

Hi Scott,

Waiting for your support. When can I get support?

Thanks.

0 Sandeep Tallada over 5 years ago in reply to Downey Kim

TI__Prodigy 520 points

Downey Kim, Sorry for the delay in response.

As per your confirmation on OTP and section 9.4 successful completion, I could not see any faults.

I would suggest :

make sure you measure the varied input voltages using multi meter across CR, CP for varied capacitor values
once you set the gain and offset values, disconnect the OWI communication and reconnect again to check the values. (Unreset the microcontroller)

1. Unreset the microcontroller.
2. Place the sensor at its minimum pressure (15 pf).
3. Start the OWI and reset the microcontroller.
4. Go to the ADC Conversion Result area, on the right half of the GUI.

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PGA400-Q1: Regardless of the capacitance value, the ADC calibration results are the same.