ADS7142: ADC power supply is bumping up

Lingaraju Erappa

Part Number: ADS7142

Hi Team,

We are using ADC "ADS7142IRUGT" in our design.

Test set-up and observation: -

The input to ADC is NTC voltage divider circuit. The pull-up voltage is 4.2V and AVDD is1.9V for the chip. Both the voltages are different.

The AVDD 1.9V changed to 2.3V once we power ON the board.

1. Kindly suggest us how to solve this problem.

2. Why this is happening.

-Regards,

Lingaraju E

Mob: +91-99868836051

4 months ago

0 Tom Hendrick 4 months ago

TI__Guru**** 170985 points

Hi Lingaraju,

Can you provide a schematic snippet showing how you have the NTC connected to the ADS7142?

0 Lingaraju Erappa 4 months ago in reply to Tom Hendrick

Prodigy 30 points

Hi Tom Hendrick,

Below is the Circuit of NTC with ADC7142 for your reference.

-Regards,

Lingaraju E

0 Lingaraju Erappa 4 months ago in reply to Lingaraju Erappa

Prodigy 30 points

Please note R350 is DNP.

0 Tom Hendrick 4 months ago in reply to Lingaraju Erappa

TI__Guru**** 170985 points

Thank you Lingaraju,

The analog input voltage to the ADS7142 has to be less than or equal to your AVDD supply (see the top of page 5, ANALOG INPUT). With 4.2V on R207 and R304 you are going to back drive through the ESD cells of the ADC to your AVDD supply. You need to change your supply voltage and/or revise your R207, R304 values such that you stay within the operating limits of the ADC.

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ADS7142: ADC power supply is bumping up