floating inputs and unpowered devices

RChapman — Wed, 25 Jan 2006 00:29:15 GMT

This message contains an entire topic ported from a separate forum. The original message and all replies are in this single message. We have seeded this new forum with selected information that we expect will be of value to you as you search for answers to your questions.

Posted: Tue Sep 27, 2005 7:11 pm

Is there any danger of floating inputs (on HC08) connected to device output that is un-powered - power have been taken away from the device via FET, but processor power still remains. This is low power state, and GP32 is but in STOP. Will the GP32 and/or the external unpowered part (output) be sufficient always without failure to keep port pin low (and therefore not floating) ???

Posted: Thu Sep 29, 2005 1:51 pm

If the HC08 variant you're using has optional pull-up resisters on the inputs enable them, place your circuit(s) in sleep-mode and see if the inputs are pulled up (to HC08 Vdd).
Alternately, you can provide external pull-down resistors. I don't think I would leave them floating.

Posted: Thu Sep 29, 2005 11:01 pm

Do not under any circumstances leave floating inputs on any digital logic. especially if you are expecting a "low power" mode.
Floating inputs can be expected to settle at the point where the port pin absorbs its maximum current.

8-bit Microcontrollers中的主题 floating inputs and unpowered devices

floating inputs and unpowered devices