ADC calculation

[harry123]

Hello, I want to convert the ADC value into voltage. Using internal ADC1 in stm32f429-disc1 board

The input voltage applied to channel 1 is 300mV

APB2 is 90MHZ

Clock Prescaler is PCLK2 divided by 4

Resolution is 12bit(15 clock cycle)

Sampling time 3 cycle

What will be the Vref and how to get to know the voltage? 

Thank you.

[Tinnagit]

Vref is tell you what value at 1.21V which 1.21V is constant Vref but it has tolerance according to the temperature.

So you can find nearest voltage from volt per bits that it calculated from Vref.

[waclawek.jan · Accepted solution]

ADC's reference is voltage on the VREF+ pin, which on the Disco-F429 is connected to VDD (see schematics in the Disco's web folder under CAD Resources tab), and that is derived from the 3V voltage regulator. The actual voltage will be somewhat lower, maybe around 2.9V, due to the series Schottky diode.

VREFINT (which is around 1.2V) is a different thing; it's an internal reference voltage which can be used in an indirect way to determine VREF+ voltage.

JW