Shop OBEX P1 Docs P2 Docs Learn Events
Safe clamping diode current — Parallax Forums

Safe clamping diode current

PhilldapillPhilldapill Posts: 1,283
edited 2009-05-18 07:06 in Propeller 1
What is the recommended clamping diode current for each Propeller IO pin? Ideally, you wouldn't have any, but when interfacing higher voltage(>3.3V) devices, there will always be a little. I am interfacing the Propeller to a Mosfet Driver chip. I have a couple of 100k pull-up resistors, attached to 12V, at each input of the driver chip. The Propeller will be driving the inputs, but I need the pull-up resistors to ensure certain states in the driver chip when no propeller is attached.

So, if I have the pull-up resistors attached to 12V, and the clamping diodes in the propeller begin clamping at 3.6V, then that means each diode will be sinking 84uA. To me, this sounds fine. Is it?

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-05-18 03:42
    That spec is in the datasheet.

    -Phil
  • PhilldapillPhilldapill Posts: 1,283
    edited 2009-05-18 04:29
    Got it. 500uA. Thanks, Phil.
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2009-05-18 07:06
    I often use the 1K resistors, for 5V interfacing. Is the quoted 500uA for one pin only, at a time, or could a bunch of them do it at the same time. Outputs often have higher individual ratings than group totals, I wonder if the same holds for inputs. How many 84uA's together???
Sign In or Register to comment.