stm32f373: stability of DAC/ADC?

• stm32f373: stability of DAC/ADC?
  Posted by exe on 09 Nov, 2018 20:50
• Dear forum,
  
  I'm building a power supply and I wonder how stable are DAC and ADC (the one that is 16 sigma-delta) on stm32f373. Do they drift much with age and temperature?
  
  Another question: if I use a separate supply for Vref, how can I ensure it never exceeds Vcc+0.4V (esp. on startup)? I could put a a diode, but it may have a bigger drop.
  
  UP on the second thought, a small-signal Schottky may do the job, but still ideas on proper power sequencing are welcome. May be I need a power supervisor or something that will only enable Vref after Vdd is up. Or, may be I can use MCU to enable Vref only after it boots and after some delay...
• #1 Reply
  Posted by iMo on 10 Nov, 2018 13:06
• The ADCs and DACs do not age/drift much. Vrefs do.
  In case your external Vref will be lower than Vcc (ie 2.5V) I would not care much about startup conditions.
  The tempco of the internal Vref is 100ppm/C (read the datasheet).
  Also mind the ext Vref+/- pins might be available with large packages only.
  Otherwise the performance of the MCU's internal ADCs and DACs is inferior to the discrete ones..
  
  PS: the temperature of the stm32's die depends on its activity. It could vary +/-xxC based on which part of your code runs at the moment..
  
• #2 Reply
  Posted by exe on 23 Nov, 2018 20:01
• Thank you very much.
  
  To my surprise, SDADC has temperature drifts specified in the datasheet. I'd say drifts are quite noticeable, especially in single-ended mode.
• #3 Reply
  Posted by lucazader on 23 Nov, 2018 23:14
• If the temp drift is specified in the datasheet then you should be able to use the on chip temp sensor to compensate for this.
  
• #4 Reply
  Posted by exe on 24 Nov, 2018 07:27
• Quote from: lucazader on 23 Nov, 2018 23:14

  If the temp drift is specified in the datasheet then you should be able to use the on chip temp sensor to compensate for this.
  

  
  The datasheet tells only typical/maximum drift, so I don't think it can be compensated without manual characterization.
• #5 Reply
  Posted by AndyC_772 on 24 Nov, 2018 08:36
• Some users have experienced 'saw tooth' drift with the SDADC on STM32F373, it's well worth doing a search to see what turns up.
  
  Here's a starting point:
  https://community.st.com/s/question/0D50X00009cd2WLSAY/stm32f373-sdadc-drift
  
• #6 Reply
  Posted by electrodacus on 26 Nov, 2018 08:24
• I use the STM32F373 in my projects for a few years and the SDADC is excellent so is the internal reference so I will not bother with an external one. I have no experience with the DAC but I suspect that should be good also it is just lower resolution.
  My projects are all open source so if you need some inspiration check my latest Kickstarter page as there is where you will find user manual for all projects and all of them have the links for SW and HW files on the last page of the manual.