Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

Output Pin Driving Another Output Pin

Hello all, I've run into an unusual problem. I'll start off by describing my goal: I'm designing a circuit that can test for short circuits and open circuits in a wiring harness. The wiring har...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

Thanks, Cris.

Here's what I came up with, as a whole. The MOSFET on the left hand side is for the transmitting end and the MOSFET on the right for receiving.

The wire connecting the MOSFETs is our wiring thats to be tested and the output from the right MOSFET is connected to the CPLD - hence, its Drain is at 3.3V.

http://i.imgur.com/PFuDZ.png

My only issue is that I will end up with a lot of transistors on the board due to this. But if you feel this is the best solution, I'll go with it.

But suppose I also want a reasonable current to flow through the harness, how would change this circuit? As it stands, the current will be very low because of the high input resistance of MOSFETs.