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JWeij.1
JWeij.1
Visitor II
February 21, 2020
Question

What is the time it takes for the STM32l082kb to wake up it's adc? and is a ferrite bead necessary?

For my new project i have to use an ADC to measure the peak value of a pulse. This pulse wakes up the microcontroller from stop mode, and the processor has to wake up the internal adc to take the samples needed. Unfortunately i can't find the time it takes for the adc to wake up in the datasheets, if the wake up time is too high i might have to consider getting an external one. Furthermore, in the hardware reference for my microcontroller there is a ferrite bead included to stabilize and filter the adc input voltage, if i use the adc it will be with a Vref of 3,3Volts and i will use the 12-bit adc to measure in steps of preferrably 10mV. I have read online that a ferrite bead is recommended and can make a big difference, but i can't find how to select the proper one.

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1 reply

Uwe Bonnes
Uwe Bonnes
Chief
February 21, 2020

For the ferrite bead in uC applications, I use BLM18RK102 or similar. It already has substanstial impedance (several 10 Ohm) already at 1 MHz, 1kOhm at 100 MHz and still over 100 Ohm at 1 GHz.

Can you use a analog peak hold circuit? Or perhaps use a BAM capable controller (e.g. STM32L4) and sample the ADC continuous via DMA and use the analog watchdog for wake up.

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