Help using the PXI-6515 for negative voltage controlled logic devices.

[kevhead891]

Has anyone tried using the PXI-6515 connected to a SCB-100/100A to directly output negative voltage to a device? I have some devices that are controlled by negative voltage where -5V input is regarded as HIGH and 0V as LOW logic. Would I connect -5V to a VCC port?

Thanks

[santo_13]

Can you share more information about your external device?

here are some important information about 6515 to consider for your application.

[kevhead891]

Hi Santo_13, 

The device I want to control in question is this one : https://www.analog.com/media/en/technical-documentation/data-sheets/hmc424a.pdf

The HMC424ALP3E attenuator.

Thanks,

[santo_13 · Accepted solution]

6515 outputs is sinking, this means, it can pull the DO line to Px.GND and not drive it to Px.COM. Good thing is that you can use the isolated nature of bank of outputs to your advantage to drive -5V.

The control bit drive circuit recommended by in the datasheet also uses simple chips to invert the logic and swap the GND and VCC terminal usage to their advantage.

Based on the above circuit and understanding of the 6515 output block diagram provided in the user manual, the below circuit "might" work.
Caution: Please try the below circuit at your own risk, to be safe, add sufficient resistors on the supply rails to not permanently damage 6515 during experiments.

If you would like to play very safe, you can use the 6515 in the intended way and include the 7404 inverter circuit provided in the data sheet like below,

[kevhead891]

Many thanks for the help santo!