What is the fastest adc sampling speed when using 4 adc's

[Taxara]

Hi

I thinking of buying and STM32WB (P-NUCLEO-WB55 evaluation board) because of the fast ADC.

I need to sample four analog signals with a rate of a few hunderd Ksps and store their values.

• what would roughly be the sample rate when using 4 adc inputs (8bit)?
• Is there any direction you can guide me to, to accomplish this? (example/ adc application note)

Thanks in advance,

[Ozone]

The datasheet for the STM32WB55CC says 4,26 Msps.

Up to 7,11 Msps with reduced resolution.

[Taxara]

Yes this seems to be the case when using one adc. But i think, (i cant really find this) that it would be divided by x when sampling x at the same time.

[TDK]

Yes, it will be x/4 if you use a single adc. Or x/2 if you use two adcs for 2 channels each. If that chip has two adcs. Still gets you well over a couple hundred ksps in either case.

[Remi QUINTIN]

​For 8 bit resolution , the fast ADC of the STM32WB can achieve up to 5.81 Msps. This let over 1.4 Msps for each of the 4 signals.

It is by far enough for the signals you want to sample.

[Ozone]

For sure, that is the way a multiplexed SAR ADC works.

I would choose the lowest sampling rate ( longest sampling time) possible, as this would ease the design of the analog input section.

In the Msps range, this is much more difficult then it seems at first glance.

[Philippe Cherbonnel · Accepted solution]

Hello,

As said above by Remi, the ADC is fast enough for your " few hunderd Ksps" application, you can even use it with resolution 12 bits.

You can refer to STM32WB reference manual for conversion time calculation.

conversion time = (sampling time + conversion time resolution) x (1/ ADC clock freq)

for example, with ADC resolution 12 bits, sampling time 47.5 ADC clock cycles, ADC clock freq 64MHz:

conversion time = 0.9375us <=> 1Msmp/sec

About examples to help you start your application:

There are several examples in STM32WB FW package (available to download on www.st.com).

Here are some examples using multiple ADC channels:

• using ADC LL driver:

...\Firmware\Projects\P-NUCLEO-WB55.Nucleo\Examples_LL\ADC\ADC_GroupsRegularInjected_Init

Convert one channel with trigger from timer and data transfer by DMA, another channel on asynchronous trigger

• using ADC HAL driver:

...\Firmware\Projects\P-NUCLEO-WB55.Nucleo\Examples\ADC\ADC_MultiChannelSingleConversion

Convert 3 channels (1 from GPIO and 2 internals (VrefInt, internal temperature sensor)) with data transfer by DMA.

Best regards

Philippe

[Taxara]

Hi Philippe

Thanks for the examples and extensive information!

Cheers,

Taxara