GPADC reference voltage connected to 3.3V, differential range ±2.1V. Is the internal reference 3.3V/2? How to calculate the valid code range and LSB for 12-bit differential mode? To receive a differential voltage of 0~3.3V, how to handle overrange? Could someone knowledgeable please advise?
- The reference voltage is not connected to the 3.3V power supply; it is generated by an internal LDO.
2. The 12-bit code range is 0-4095, corresponding to an input differential voltage of approximately -2.1 to 2.1V, so the LSB is approximately 4.2V/4096. Note that these are approximate, not precise.
- I want to confirm what kind of signal the 0-3.3V differential voltage you mentioned is. Are the P and N common-mode voltages the same? Is the signal DC or high-speed AC? If you are just measuring the differential of a single-ended signal to GND, you can use our single-ended test mode, which is calibrated and can measure precise DC or slow voltage. The single-ended measurement range is 0-3.3V.
Vcm=1.65V, high-speed AC signal
For the differential signal spanning -3.3 V to 3.3 V, we still need to find a way to limit the input to within the input range. Depending on speed requirements, you can consider using a small-value resistor voltage divider or driving it with an op amp.