Cannot find a good solution, P-CH MOSFET Array

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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:
http://docs-europe.origin.electr...

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?
:idea::idea::idea:

Many, many thanks for any help!

Attachment(s): 

Just a noob in this crazy world trying to get some electrons to obey me.

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http://www.allegromicro.com/en/P...

I don't know of a driver with inbuilt shift registers off the top of my head. Maybe have a look at OnSemi.

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Kartman wrote:
http://www.allegromicro.com/en/P...

I don't know of a driver with inbuilt shift registers off the top of my head. Maybe have a look at OnSemi.


Hi, those drivers are great! I have used them before and really like them, but the problem is they are darlington pairs, so the VCE saturation voltage is like 1.4V, which would drop my 5V to drop to 3.6V!
But something like that with MOSFET outputs or even relay outputs, or anything with low V drop would be perfect.

I browsed around your link thanks Kartman! Found all sorts of LED drivers, but all sinkers. Glad to see you still here helping the masses out! Thanks!

Just a noob in this crazy world trying to get some electrons to obey me.

Last Edited: Tue. Jun 29, 2010 - 03:04 PM
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After many many hours of searching I found the perfect IC (made by ATMEL no doubt), but its discontinued!!! Why!

Check out this bad boy:
6 x PMOS and 6 x NMOS, 0.6A/40V each, and SPI interface. What a dream.
http://docs-europe.origin.electr...

Just a noob in this crazy world trying to get some electrons to obey me.

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How about this bad boy: http://www.st.com/stonline/produ...

Seems to fit the bill very nicely.

Edit: disregard that, it doesn't fit at all.

Last Edited: Tue. Jun 29, 2010 - 08:29 PM
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Quote:

After many many hours of searching I found the perfect IC (made by ATMEL no doubt), but its discontinued!!!

I don't see that on this page:
http://www.atmel.com/dyn/product...

...but it doesn't seem to be in the distribution channels. My Octopart search seems to indicate that this device is/was available from other manufacturers as well.

The ATA devices might be a bit "newer"--isn't the e.g. '6836 close?

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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Quote:
Hi, those drivers are great! I have used them before and really like them, but the problem is they are darlington pairs, so the VCE saturation voltage is like 1.4V, which would drop my 5V to drop to 3.6V!

Then crank up the volts! The 2981s do the level translation for you. If its for a multiplexed led display, then I would normally run 12V for the leds ( multiplexed and with limiting resistors). Might be cheaper/easier than your other options.

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I might not have misread this one :)

AMIS-39100: Octal High Side Driver with Protection

http://www.onsemi.com/pub_link/C...