STM32F1 PC13 LED

• STM32F1 PC13 LED
  Posted by ipek.grgc on 15 May, 2020 13:47
• Hello everyone, hope you are doing okay.
  
  In STM32F103C8's datasheet, Rev 17 page 33, it says:
  
  " PC13, PC14 and PC15 are supplied through the power switch. Since the switch only sinks a limited amount of current (3 mA), the use of GPIOs PC13 to PC15 in output mode is limited: the speed should not exceed 2 MHz with a maximum load of 30 pF and these IOs must not be used as a current source (e.g. to drive an LED). "
  
  But, as far as i know, in Blue Pill's design PC13 is driving a LED. How come? I am wondering.
  
  Thanks! Be safe.
• #1 Reply
  Posted by exe on 15 May, 2020 13:57
• Nice catch. I guess this answers it: https://electronics.stackexchange.com/questions/440929/current-sinking-with-pc13-on-stm32f103c8t6 .
  TL;DR: the current supposed to be within the limits if the board is done properly. But I can easily imagine that knock-off clone would violate this.
• #2 Reply
  Posted by Jeroen3 on 15 May, 2020 14:25
• Also, in the bluepill schematic PC13 is in sink configuration, not source. I suspect impact of sink is a lot smaller compared to source.
• #3 Reply
  Posted by exe on 15 May, 2020 20:13
• I think that text from the datasheet is inaccurate. Long below that I found this text:
  
  > The GPIOs (general-purpose inputs/outputs) can sink or source up to ±8 mA, and sink or
  source up to ±20 mA (with a relaxed VOL/VOH) except PC13, PC14 and PC15 which can
  sink or source up to +/-3mA.
  
  Page 65: https://www.st.com/resource/en/datasheet/stm32f103c8.pdf