Keithley 2651A Reference Manual page 134

Model 2651A High Power System SourceMeter® Instrument Reference Manual
Timers must be used to configure the pulse width and period. Refer to
mode sweeps
The pulse width is managed by controlling the duration between the source stimulus event and the
end pulse stimulus event. Note that a latency exists between these stimulus events and their resulting
source level transitions. This trigger latency can vary based on factors such as the source range and
the electrical characteristics of the device under test (DUT). The fast ADC mode can be used to
characterize this latency, in order to better control the shape of the pulse under a particular set of test
conditions.
The figure below shows the source and end pulse stimulus events in relationship to the pulse. Any
change in Δt will result in a corresponding change in the pulse width.
Pulse duty cycle
Duty cycle is the percentage of time during the pulse period that the output is on. It is calculated as
follows:
For example, if the pulse width is 10 ms and the off time is 90 ms, the duty cycle is calculated as
follows:
Duty cycle
See Maximum duty cycle equation
maximum duty cycle for a SMU.
2651A-901-01 Rev. A / March 2011
(on page 3-45) for details.
Figure 40: Pulse width control
Pulse level
Source stimulus
event detection
Bias level
Duty cycle = Pulse width / (Pulse width + Off time)
= 10 ms / (10 ms + 90 ms)
= 10 ms / 100 ms
= 0.10
= 10 percent
(on page 4-4) for additional information on calculating the
End pulse stimulus
event detection
Δ
t
Section 3: Functions and features
Using timers to perform pulse
3-27