AD7768-1 analog input overvoltage protection?


- does the AD7768-1 have internal ov-protection diodes between the AINs and AVDD1?
- what is the maximum rating on the current handling of these diodes?

- I want to have AVDD1 = UREF = 5V. Is this allowed? Does this degrade performance somewhat?
- under this condition, does the precharge buffers on AIN and the reference buffer still function properly?

Thanks for help.

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[edited by: NiallM at 2:24 PM (GMT 0) on 14 Oct 2019]
  • Hi Alex,

    There are internal protection diodes on the analog input pins. Figure 63 in the datasheet shows how these are set up. These diodes are not designed to withstand any disturbance for a prolonged period of time, more so for ESD. You should add protection diodes if there is a chance the AD7768-1 will see inputs outside the absolute max ratings specified.

    AVDD1 = VREF = 5V is a valid configuration. You can see the INL plot in Figures 22-24 for various reference voltages with no major degradation in INL. You may see some small differences in performance such as a small change in THD. You should note also that the supply to the ADC driver amplifier may need to be increased for extra headrooom if using a 5V reference.  The precharge buffers and reference buffer are designed to handle 5V.