I would like to supply serial data directly to a CMOS chip from an 81142A pulse data generator. The chip expects Vlow = 0 and Vhigh=1.2V.
I have read through the manual which describes the protection algorithms applied to ports which are not connected, and that if an improper impedance (not 50 ohms) is detected then the voltage is automatically set to a safe level for the instrument. I also noticed that none of the available preset logic families listed in the user guide apply to my device. Given that my device will not show anything close to 50 ohms to the generator port, can I expect to give this instrument to give me the voltages I want, or will the instrument see too-high impedance and kick in the protection? Furthermore, how far away from 50 ohms is "too far" is not made clear in the user guide, unless I'm missing something.
Thanks in advance.
I have read through the manual which describes the protection algorithms applied to ports which are not connected, and that if an improper impedance (not 50 ohms) is detected then the voltage is automatically set to a safe level for the instrument. I also noticed that none of the available preset logic families listed in the user guide apply to my device. Given that my device will not show anything close to 50 ohms to the generator port, can I expect to give this instrument to give me the voltages I want, or will the instrument see too-high impedance and kick in the protection? Furthermore, how far away from 50 ohms is "too far" is not made clear in the user guide, unless I'm missing something.
Thanks in advance.
the data output is designed and relies on the fact that it is terminated by 50 Ohm.
Please see the attached Datasheet and also User Guide page 72, etc.
Anything else will lead to problems:
• you will get reflections back from your DUT (impedance not matching) into the 81142A.
The how much and when depends on what the mismatch is and the length of the cables, frequency, etc
• The voltage settings are assuming 50 Ohm termination. Anything other than 50 Ohm
requires carful operation and manual adjustment. The best is to start with a an amplitude setting of less than
100mV in order to see how the system reacts81141A-UsersGuide.pdf81141A Data Sheet 5989-3052EN.pdf