Choosing clock source for ADC

[mohamed_husain]

Hi There,

I am using STM32C031C6 evaluation board. I am using ADC_IN1 for the ADC measurement. I want to use internal clock source for my board. I want a stable ADC output. 

1. Which internal clock source should I choose for the stable ADC output?

a) HSI48 (48 MHz)

or

b) LSI (32 kHz) 

STM32C031C6 has sampling rate of 2.5MSps. I am going to use less samples. I want a stable ADC output. 

Kindly give your suggestions and answers. Thanks in advance!

[AScha.3]

Hi,

HSI48 , or (best) HSE (also 48M).

[mohamed_husain]

Thanks @AScha.3 !

Unfortunately, I want to use Internal Clock Source. HSE is an external source.

[TDK]

Use the default 48 MHz HSI48.

[SofLit]

Hello,

I want a stable ADC output. 

---

What do you mean by stable? how much?

According to the STM32C031 datasheet these clock sources jitter depends on the voltage and the temperature.  So you need to assess this "stability" according to your final product environment/needs.

[mohamed_husain]

The table shows the frequency produced by the oscillators and its characteristics. 

I want to measure accurate voltage given to ADC_IN1 pin. The measurement should be accurate and stable.

[SofLit]

Hello,

I thought you were referring to "sampling jitter" not the stability of the conversion. In that case you can refer to the AN2834 "How to optimize the ADC accuracy in the STM32 MCUs".

Check your VDDA/Vref+ power supply. The averaging samples is one of the technics to get more stable conversion.

[Jacob WOODRUFF]

Hi All,

This question has been routed to our online support center for direct support.

Regards,
Jake

ST Support