I have a question about USB-6501, specifically about the Fig.5 of NI
USB-6501
User Guide and specification. Lets say my RI is 200 Ohms. If I follow your
procedure and I want to achieve 8.5 mA I have to set up Re to 423 Ohms.
This
will give me 8.5 mA to RI load. Accordingly to your specification the circuit connected to Port Pad is open drain transistor. If I operate that circuit my current from internal source will be 5V divide by parallel combination of
423
Ohm and 4700 Ohm resistors. The resulting current will be 12.8 mA which is
not allowed.
So by following your procedure I created self destructive circuit.
Am I missing something? Please send me explanation to this. The second question is what is maximum current handling capability of the open drain transistor? Is it also 8.5mA or is it higher?
