programing ni 6556 channel (DIO and PFI) to be on high impdance or tri state

[NR_leo]

Hi,

I have serious problem of leakage currents from ni 6556. While I am trying to activate an ASIC with specific mode of operation and measure the current consumption.  The source of the problem is one of the outputs of the ASIC, which connect to ni 6556 (DIO channel and PFI channel as well). When this the output is connect to the 6556, I measure current consumption of 120 uA, and when I disconnect this output, I receive current consumption of 40 uA.

Unfortunately, this measurement of current consumption is a routine test and I cannot disconnect the specific output as a routine. (The test is done on a probe station with probe card, to disconnect the specific output I need to do manual probbing).

I tried the following 3 methods:

1. Defined all unnecessary channels in 6556 as stPMU current source of 0 uA- this didn't change the current leakage.
2. Program all unnecessary channels in 6556 to be in high z (with nihsdio property node) - this also didn't change the current leakage. (Attached picture of the VI)
3. Defined all unnecessary channel in 6556 to be in tri- state .In this method I didn't succeed to program the PFI channels (I received an errors, when I tried to set this PFI channel in tri state) .

Can someone tell me how to program the 6556 channels to be "disconnected"?

Thanks Harel 

[scmave]

Can you clarify which channels you're wanting to "disconnect"? Are you wanting the channels that are used for the ASIC test to close during the current consumption test? If so, I think what you're looking for is a switch to remove the hard connection.

Or are you trying to "disconnect" the unused channels hoping that would remove the possibility of leakage? If so, I don't think that this will be the source of the current consumption.

Finally how are you testing the current consumption, and how are you disconnecting the output of the 6556 to get 40 mA?

[NR_leo]

I measuring the current consumption by dc power smu (ni 4141), which suply dc voltage (vdd) for the ASIC.(I program it to be voltage source and measured the current..).

To get low current consumption I disconnect one of the hard switch in the PCB (physical switch ) that connect output of the ASIC to  dio1 and PFI1  channel of 6556. (unfortunately I need to make this test as routine test in another PCB, in which I don't have this physical switch that I need to disconnect, so I try to disconnect those channels  "programmably").

thanks Harel   

[scmave]

If setting the channel to high-impedance is not enough to close the connection then you'll need to physically disconnect the device from the DUT. So, there isn't going to be a way to disconnect the connection to the 6556 unless you have a physical switch unfortunately.