ADS7828: ADS7828

joshua Ayres

Part Number: ADS7828

I am using ADS7828EB/2K5 in my design to measure external voltages but my readings fluctuate because the IC's Vdd (+5V) changes +- 0.1V. Is there a way I can measure Vdd or measure the chips internal voltage reference (2.5V) to then calculate what my true Vdd is and then use a more accurate Vdd in my software? In summary, I would like to gather a more accurate Vdd to use in my software instead of a fixed 5.00 V.

9 months ago

0 Tom Hendrick 9 months ago

TI__Guru**** 171005 points

Hi Joshua,

You can measure the internal reference at pin 10 of the ADS7828. That should still be a stable 2.5V source even if your Vdd supply varies by +/-100mV. What does your schematic look like on the ADC inputs? Do you have any buffers ahead of the analog inputs?

0 joshua Ayres 9 months ago in reply to Tom Hendrick

Prodigy 20 points

Hi Tom, thank you for responding I hope I can use your advice. I looked at the data sheet though and I am unsure how to do measure pin 10? Using page 11 from the datasheet, how are we able to address pin 10's voltage? I only see how you can ask for Ch0-Ch7 voltages.

0 Tom Hendrick 9 months ago in reply to joshua Ayres

TI__Guru**** 171005 points

I was thinking you would measure the reference voltage at pin 10 with a multi-meter. The reference does not have direct input to any of the channels.

0 joshua Ayres 9 months ago in reply to Tom Hendrick

Prodigy 20 points

Gotcha! If I turn on the reference voltage pin will all of my ADC channels need to be below the 2.5V?

0 Tom Hendrick 9 months ago in reply to joshua Ayres

TI__Guru**** 171005 points

The input range for the ADS7828 is 0-Vref, so if you use the internal 2.5V reference, any input above 2.5V will clamp at the full-scale code.

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ADS7828: ADS7828