dissipation or sink current for PXI-6551

[ajog]

I'm unable to drive a line low with the PXI-6551.  The line has a 250Ohm pull-up to 2.5V.  The PXI-6551 detailed specification sheet or the HSDIO help does not have this information.  The max drive current for PXI-6551 is 50mA but does anyone know how much it can sink/dissipate?

Anand

[Aaron_W.]

Anand,

I looked into the Specs as well, but was unable to determine an exact value that the device can sink. Are you able to drive the line low when you take out the pull-up circuitry on the line? I will check and see if there is a reason why we don't spec this, it may be possible that the device is not designed to source current. 

[Keith.Shapiro]

The PXI-6551 should be able to both source and sync 50mA per channel.

2.5V to GND across 250 ohms should only result in 10mA, so you should have no trouble driving a low value.

Can you post your VI, and possibly a diagram of how you have the PXI-6551 hooked up?

Thanks!

Keith Shapiro

National Instruments R&D

[ajog]

Thanks Keith,

I think the problem is with our test board and some rogue ICs.  By removing them and testing the DUT directly with the 6551 we observe expected behavior.  Sorry, but I should have informed the forum as soon as the matter was resolved.

Anand

[Keith.Shapiro]

Glad to hear everything is working for you, Anand.

Let us know if you have any more troubles.

Keith