+5V output dropout

[cnardo]

My NI OEM USB-6211 when connected through its 50pin connector to a pcb board seems not be able to provide the +5V output anymore. The output provided voltage is about 1,5V instead of the declared +5V, without any analog or digital output activated on OEM USB-6211.

One possible explanation could be that the pcb board overloads the OEM USB-6211, even if theoretically the pcb board should require less than 50mA (the max current declared in the OEM USB-6211 specifications).

In order to check that my OEM USB-6211 is OK (not broken) and it is able to provide +5V output with a load of max 50mA I could connect the +5V output pin to DGND through a resistor (e.g. 100R). Decreasing the resistor value I should notice that OEM USB-6211 is not able to guarantee +5V anymore. Of course these test should be run without any other connected pc board. Does this test make sense or should I try differemtly?

Thanks.

[crossrulz]

It is generally not a good idea to power circuits with the +5V line.  It is there mostly just to supply a pull up if needed.  I'd say if you can measure the +5V without the pcb board, the 6211 is fine.

Also, be careful because that 50mA limit is shared with the DIO lines as well.

[cnardo]

Thank you for the answer. That means I cannot use the +5V as supply for a pcb board connected to NI USB-6211.

How can I supply the pcb board? It needs +5V and -5V dual supply and less than 50mA current.

Is it possible to use some IC that "stabilize" the +5V before using it to supply the pcb board?

Thanks.