I'm using BL702 with VDDCORE, AVDD33_AON, AVDD33_PA powered from 2.5V power source.
Reference manual states, that there is only two choices for ADC reference voltage: 3.2V and 2.0V (no external reference is possible):
Using current bl_mcu_sdk HAL library for ADC interaction and ACH_CH7 connected to 2.5V through pull-up resistor I'm getting accurate 2521 mV value while reading ADC data. How could it happen?
I supposed, that AVDD input is used as ADC reference voltage. So in described conditions I supposed, that I shall get about 0xFFF (full scale saturated value) for 12bit conversion mode (2.5 V input with 3.2V external reference, having actual 2.5V reference value). But it seems, that BL702 has internal charge-pump for ADC reference generation or something like this.
Could somebody explain my case? What is actual ADC reference value with 2.5V MCU power voltage?