What is input equivalent circuit of USB 6009 PFI0

[kscholl]

Is the USB 6009 PFI0 input the same as the analog circuit input shown in the user manual?

I am using the PFI0 to trigger a voltage measurement and it works great using an HP function generator.

When I try to drive the input low with my circuit it looks like there is a pull up resistor to +5 on the PFI0 input terminal.
Will this PFI0 input accept a 0 to 15 volt comparitor output with being damaged?

Kip

[kscholl]

After looking at the user manual again, I am guessing that the PFI0 is speced as the other digital input teminnals with a 4.7k resistor to +5. Can you confirm this. Looks like I will have to convert my cmos digital output to TTL.

Can any body confirm this?

[kscholl · Accepted solution]

Here's my solution to drive the PFI0 TTL digital input using a CMOS comparator.

I am using a 2N4401 npn transistor. 

Connect the Emitter to the ground terminal.

Connect the Collector to the PFI0 terminal (there is a pull-up resistor internal to the 6009).

Connect the Base to a voltage divider that limits in input current and drops the CMOS voltage to TTL levels.

In my case I am going from 0 to +15 so my voltage divider is 4.7k and 2.2k ohms to drop it down to 0 to +5 volts.

This is an inverting circuit so your trigger sense will change from rising edge to falling edge, or vice versa.

I hope this helps someone out.

Kip