PCIe-6537 Input Capacitance

[nickstorton]

Hi,

I have an application that is very sensitive to capacitance and wondered if anyone knows what the input capacitance of the PCIe-6537 is?

Thanks

Nick

[NI-MarkN]

Hi Nick,

The capacitance of any NI HSDIO device and cable combination is dominated by the capacitance of the cable, as the input capacitance of the HSDIO device channels are minimal.

The PCIe-6537 device capacitance is determined by the buffer component before the output and input. You can find the buffer part number on the actual PCIe card on the side. The ones used in this device are NC7WZ126 TinyLogic UHS Dual Buffer with 3-STATE Outputs from Fairchild Semiconductor. You can find the link to the datasheet here: https://www.fairchildsemi.com/ds/NC/NC7WZ126.pdf

If you scroll down to page 3 of the datasheet you can see from Cin, Cout and Cpd values that the capacitance per channel will vary between 4 and 10 pF.

Hope that helps.

[nickstorton]

Hi Mark

Thanks for the quick reply, that helps a lot. Do you have any info on the cable capacitance?

Thanks again,

Nick

[NI-MarkN]

Hi,

No problem at all.

A default SHC68 cable will have a capacitance of approximately 100pF (that's including the connector leads as well).

[QiongW]

The input also has 40ohm resistor in series, and then around 12pF to GND, in parallel with a 50Kohm, so the equivalent model looks like

1m VHDCI cable capacitance is around 100pF