Hi, many thanks for the further clarification of your questions. I think you have to be careful not mixing here different things with one another. to your 1st question: From the user's perspective there is not much to care about +Vs and -Vs with the inputs A1.5-A1.7. As described in the User's Guide, these are all internal signal sources for the ADC. A1.5 is connected to an integrated resistive voltage divider, which gives you the possibility to measure the device supply voltage without any additional external components. If the device is supplied from a battery without an LDO, this means you can measure the battery voltage. A1.6 is connected to the internal temperature sensor, which allows you to measure the chip temperature. Due to the low power consumption and thus low heating up of the device itself, it is usually very close to the ambience temperature. Finally A1.7 is a short on the positive and negative input. This allows you to measure the offset of the PGA, as in ideal case the result should be 0. to your 2nd question: As described in the section of the User's Guide, which you pasted in, in this very section right about the formula for the calculation of the Vfsr you can see the example is based on the built in reference of 1.2V to your 3rd question: As in my original post and the datasheet specification of the applicable input voltage ranges, the input voltage is dependent on the following factors: a) Used voltage reference. This can be either the built in reference. In this case typ. 1.2V, or an external reference, which can be, as specified in the datasheet 1.5V max. b) Selected Gain of the PGA. c) ADC mode selection Bipolar mode or Unipolar mode. As according to the formula +Vfsr = (1.5V/2)/1 = 0.75V, plus as described in the UG and datasheet, the input voltage should not exceed 80% of the maximum applicable voltage, you'll never be able to apply 1.8V directly. Best regards Peter
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