Hi, I have been trying to find an elegant solution for my problem for about 4 months now. But I have been stumped. I know there must be a way out there!!
I have these different devices that connect to a common connector. Whoever these different devices have different pin outs. The power pins are not always in the same place (and the devices draw about 150mA). So I have to make my interface connection be able to drive any one of the 24 lines to 5V, or sink any one of the 24 lines to GND.
And additionally I have to build many of these interface units. So I need to find a simple solution, or else I will spend my days and nights soldering millions of tiny MOSFETs with gate limiting resistors, and default pull up/pull down gate biasing resistors.
You can see my original schematic attached below...
What a big mess!
I learnt from Kartman on this forum about MOSFET serial to parallel shift registers earlier. These things are great, basically it combines the shift register and a N-CH MOSFET array. Great! That handles the sinking of the 24 lines to GND. I am using a TPIC6B596DWRG4, you can view the datasheet here:
But now I need to be able to pull up the 24 lines to Vcc. Unfortunately you dont get P-CH MOSFET arrays (commonly) available. So I was thinking of driving the gates of the them Vthreshold above the MOSFETs drain (like charge pumps do). But because it is an integrated circuit, one is very restricted in how one can connect up the array. Vcc for the gate control circuitry of the TPIC6B596DWRG4 can be a max of 7V. Which I dont think is high enough to turn on the N-ch MOSFETs sourcing current at 5V.
Please see the attached picture of the output stages.
Can anyone see a good solution with a low component count for switching 24 lines to 5V with minimal IO lines? Or how to use a TPIC6B596DWRG4 to Source 5V?
Many, many thanks for any help!