2: Connections Model 4200A-SCS Pulse Card (PGU and PMU)
2-24 4200A-PMU-900-01 Rev. B March 2023
Load-line effect compensation (LLEC) for the PMU
Load-line effect compensation (LLEC) is only performed for standard pulse I-V testing using PMU
measure ranges. It is not performed when using 4225-RPM measure ranges (≤10 μA). The active
RPM circuitry provides its own analog LLEC (assuming there is a short cable from the RPM to
the DUT).
The basic pulse output system is a series circuit that consists of the pulse generator resistance (fixed
at 50 Ω), interconnect (cabling and pin-to-pad) resistance, and the resistance of the DUT. In this
series circuit, the sum of the voltage drops across these components is equal to the output voltage of
the pulse generator. Therefore, if the resistance of the DUT changes, the voltage seen at the DUT
also changes. This effect is called the load-line effect. See
DUT resistance determines pulse voltage
across DUT (on page 4-17) for details on how the resistance of the DUT affects the voltage across it.
For example, consider a PMU set to output voltage to a 50 Ω load (DUT). For this default setting, the
pulse card outputs twice the programmed pulse voltage. If the interconnect resistance is negligible
(0 Ω), half the pulse card voltage appears across the internal pulse card resistance (50 Ω) and the
other half (which is the programmed pulse voltage) appears across the 50 Ω DUT. For example, if the
pulse card is programmed to output a 5 V pulse, the pulse card sources a 10 V pulse. Five volts will
drop across the internal 50 Ω pulse card resistance and 5 V will appear at the 50 Ω DUT.
The 4225-RPM also exhibits the load-line effect. The RPM has resistance in series with its output
(typically between 20 Ω and 50 Ω).
Descriptions of the LPT functions discussed in the following topics are provided in Model 4200A-SCS
LPT Library Programming.
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