If I use an external reference, can I use the ADC input pins diodes to clamp the signal? I would obviously have a 2k impedance in series.
I have not seen feedback on the AM335x ADC. In addition, I wanted to verify:
Is there any issue with using a 1.25V reference (VREFP) and ADC power will be the nominal 1.8V? All the evaluation boards use these power buses connected together at 1.8V.
The ADC input pins diodes are not intended to be used for DC clamping the signals; Rather for ESD protection. They clamp at about 2.75 V (With a 1.8 V supply) which is higher than the max recommended input voltage which is 2.1 V. The 2K in series helps limit the diode current to a safe value which should not exceed 25 mA.
No issue with using 1.25 V VREFP. However, your input signal dynamic range should be within VREFP-VREFN.
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