I am using the STM32WB55 ADC with the internal reference VREFBUF set to 2V5. To save power consumption, the application disables VREFBUF before going to sleep and enables it just after waking up.
The problem is that I am making measurements with the ADC just after wake-up and I am getting results slightly lower than the real values.
When I enable VREFBUF I do the active wait for the VRR flag and I see that it takes about 50us to settle. On the VREF+ pin I have a 100nF capacitor. If I do a delay of 500us then, the measurements with the ADC are correct.
What could cause this difference in the measurements? Why is the stabilisation time of VREFBUF so low?
