Tool/software:
Hi Team,
One question on description of reference buffer, buffer is recommended to be disabled when REFP at AVDD, I would like to figure out why we suggest this way connection, as without buffering, the reference input impedance is approximately 250 kΩ, which is much smaller than other ADCs, and risk in power consumption and stability, thanks for your help!
Hi Shengyue Zhang,
We suggest to disable the reference buffers when the absolute voltage on any REFx pin is near the supplies (AVSS or AVDD) because the buffers themselves have difficulty driving to those voltages. You can see this in the recommended operating conditions (copied below), where the REFP buffer max voltage is AVDD and the REFN buffer min voltage is AVSS. If the applied voltage on REFP or REFN changes even a little bit (greater than AVDD or less than AVSS), the buffer output will become nonlinear and the conversion results will be inaccurate
If you need to drive a voltage into the REFP pin that is equal to AVDD and the unbuffered ref impedance is insufficient, consider using an external buffer.
-Bryan
