AURIX™ Forum Discussions

[User22281]

Dear Aurix Experts,

I would like to measure the different supply voltages in TC36x devices for health monitoring (VEXT, VDD, VDDP3, VAREF1, etc). Should I use the EVADC for this? Are there specific channels for these measures?

In addition, I would like to convert raw values to millivolts for the sampled analog channels. All examples provided in Aurix Studio seem to use raw values only. How can I translate raw values to millivolts? Please note that applying a fixed factor is not an option (read next sentence).

To avoid conversion errors due to fluctuations in VAREF1 and obtain more accurate results, I was thinking of measuring VAREF in order to apply a dynamic conversion factor, instead of hardcoding a factor of 5.0V or 3.3V. Is this the correct way to go?

Thank you very much.

[NeMa_4793301 · Accepted solution]

The power rails do not have a direct connection to the EVADC. You can use the secondary voltage monitor to check the power supplies, via the EVRMONSTAT1 register. The ~2% accuracy is listed in the Supply Monitors section of the datasheet (e.g., VDDP3MON).

You can't directly measure VAREF1, but you can bring the same precision internal bandgap that drives the secondary voltage monitor into the EVADC: see 32.12.5 On-Chip Supervision Signals on page 1233 of AURIXTC3XX_um_part2_v2.0.pdf, Vmts. Because Vmts is fixed, you can use it to infer the value of VAREF.

You can also use CH0 of each converter as an alternate reference: see GxCHCTRy.REFSEL on page 1175.

To minimize conversion errors, follow the guidelines in AP32362 (A/D converter supply and PCB design guidelines for TC3xx) and AP56003 (ADC Analog Aspects).

Values are always based on full scale 4095 counts = VAREF. So, the conversion is mV = reference in mV * result / 4095.0.