ADC128S102: Input Protection Cross Channel Impact?

WolfHort

Part Number: ADC128S102

Tool/software:

The datasheet for the device says it can handle up to VA+0.3V inputs and even higher if current limited to under 10mA.

I have two inputs to the ADC, that at worst case tolerance stackup could be as high as 5.35V (separate power supply, sequenced to be after VA... But much less precise). These inputs pass through a 100Ohm series resistor before reaching the ADC128S102.

So in theory they could have input current around 3.5mA each, which seems acceptable.

However, I do not want these inputs negatively impacting other channels...

Would this configuration have any negative impact on sampling other channels of the device?

4 months ago

+1 Joel Meraz 4 months ago

TI__Expert 6620 points

Hello,

I'm assuming that your supply voltage will be 5V. The 10mA current max is due to an internal ESD diode present on the analog input to analog supply that protects from overvoltage conditions at the analog input. This diode has a nominal typical 0.5V forward voltage, but in lab, it tests at around 0.7V. Realistically, 5.35V won't pose an issue (assuming VA = 5V). If there are cases where you suspect the diode will conduct some current, it will be best practice to keep this current at <1mA to maintain the longevity of the device.

I hope this FAQ can clarify some points for you. In general, it goes over conditions that might cause your analog input voltage to exceed the analog supply voltage. Point 2b will be the most relevant in your case.

https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/1086751/faq-adc128s102-sep-can-i-apply-input-signals-before-the-analog-supply-va?tisearch=e2e-sitesearch&keymatch=adc128s102#

Regards,
Joel

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ADC128S102: Input Protection Cross Channel Impact?