Other Considerations
23
SBAU289 – October 2017
Copyright © 2017, Texas Instruments Incorporated
Precision Signal Injector EVM (PSIEVM)
7
Other Considerations
7.1
Output Impedance
The output for the single ended and differential both have the option to populate output resistance. This
feature can be used to help the PSI drive a capacitive load or to help minimize reflections through the
coaxial cabling. Typically, a 50-
Ω
resistor for the output resistance will improve stability for driving a
capacitive load and matches the impedance of the coaxial cabling. Note that by adding output resistance,
there will be a voltage divider from the output resistance of the PSI and the input resistance of the DUT.
The PSIEVM is fully calibrated with R53, R59, and R100 as 0-
Ω
resistors.
7.2
Cable Selection
It is best practice to minimize the length of the cabling used between the PSI and the DUT. It is also best
to ensure a properly tightened connection between the SMA and the coaxial cable. A loose connection
can lead to a low-quality signal transmission. The use of a torque wrench can help to ensure consistent
tightness.
