STM32L4.. fs=10Ksps ADC Current, how do you get the stated 16uA?

[gregstm]

In the data sheet it states that the ADC current at fs=10Ksps is 16 microAmps. I'm struggling to get the current that low. Even just switching on the ADC and its regulator exceeds that value

My application has a mode where I need the ADC data passed through to the DAC (unchanged) with the lowest current possible (coin cell application). Sample rate is 16,384Hz derived from TMR2 (with LSE=32,768Hz). I trigger the ADC with TMR2 and DMA the result straight to the DAC. The system clock is MSI=1 MHz , with the CPU in LPSLEEP.

Anyway, since this 10Ksps= 16uA is stated in the data sheet, I thought maybe the ST engineers could state how this current consumption could be achieved,

thanks

[Mohamed Aymen HZAMI]

Hello,

Can you please share with us the configuration that you use.

Best Regards,

Mohamed Aymen.

[gregstm]

Thankfully I think I have figured out what is going on.

It is not the ADC, drawing the unexpected current - it is the DAC. I didn't realise that the DAC consumes different amounts of current depending on what value is written to the DAC . I did my initial current tests with the DAC value/code = 0, this seems to consume minimal current. When the analog power is enabled the, DAC is mainly around a value of 2048. This DAC value seems to consume around 200 uA more. (I configure the DAC to have the Buffer=OFF, I write directly to the registers for configuration)

I would be curious to know if there is a formula to calculate the DAC current consumption for a given DAC value/code.

thanks.

[S.Ma]

Welcome to the analog world. Consumption will depend on the analog impedence of what you drive as circuitry

[gregstm]

Thanks - the Analog world is interesting. I'm pretty sure the power consumption variation is of the DAC itself, that is, the internal R-2R resistance ladder. The amplifier I was driving during testing has a 4pA input bias current - and the DAC was just set to a constant value/code during current tests. When I load another board later I will re-confirm current measurements with just the micro only loaded.