Can I use NI9476 with 5V external supply? Fixture incorrectly built that way.

[MCL_engineer]

We made a mistake designing a test fixture that interfaces to

the NI9476.  The NI9476 specifies an external supply voltage

between 6V and 36V.  The test fixture provides 5V to the

NI9476 and seems to work fine.  A redesign of the test fixture

would be difficult because 8 inputs can't handle an input

greater than 5 volts.  Does anyone know what limits the

external supply input range to 6V and if there would be any

problem leaving the fixture as is with a 5V external input

voltage?

[MCL_engineer]

I should have mentioned that all outputs of the NI9476 are driving <1mA loads.

[memoryleak]

The drivers used on the outputs of the 9476 impose this requirement, so sadly the 6V spec is an important one 😞  They aren't guaranteed to work at 5V.

For your lines that can't handle more than 5V, you might consider a different output device than the 9476 (does the 9401 meet your requirements?).  If you're already re-working your test fixture you may be able to translate the 6V+ output from the 9476 down to 5V using an external comparator or bus translator.

http://para.maxim-ic.com/en/index.mvp?tree=comparators

Hugs,

memoryleak 

Message Edited by memoryleak on 08-06-2009 10:59 AM

[MCL_engineer]

The drivers used on the outputs of the 9476 impose this requirement, so sadly the 6V spec is an important one  They aren't guaranteed to work at 5V.

For your lines that can't handle more than 5V, you might consider a different output device than the 9476 (does the 9401 meet your requirements?).  If you're already re-working your test fixture you may be able to translate the 6V+ output from the 9476 down to 5V using an external comparator or bus translator.

http://para.maxim-ic.com/en/index.mvp?tree=comparators

This link didn't work for me.  Do you have a part number for the drivers?

I'm not sure that we have the resources to do a re-design (time, money, or people), so

if the setup is working for us, is there any risk of damaging the 9476 by providing a

5V external supply?  Also, this product will be low volume for the forseeable future.

By low volume, I mean tens of products per year.  We'll only be running the fixture

at room temperature as well.

Any further information would be appreciated.

[Doiron]

Hello,

While this is obviously not officially supported due to being out of specification, I see absolutely no reason from the desgin shown in the specifications why this wouldn't work.

Have you tested this? The bottom line: it's not officially supported but if you test it and it works, go for it.

[Doiron]

Hello,

After some more investigation and some help from our friend memory leak we found that that as he mentioned, the drivers on this card are what require this voltage (>6V), so it's likely that if you are not providing the proper voltage then you will see the card working intermittently if at all.

Therefore I highly recommend a redesign or switching to another model (the NI 9474 can use a 5 V supply and should be interchangeable with your code, the big difference is channel count).