Model 2657A High Power System SourceMeter® Instrument Reference Manual
Section 3: Functions and features
2657A-901-01 Rev. B/December 2012
3-63
Output characteristics
:
•
In addition to trigger events from other trigger objects, the
digio.trigger[
N
].assert()
and
tsplink.trigger[
N
].assert()
functions generate a low pulse for the programmed pulse
duration if the line is latched low, a falling edge does not occur.
•
A normal falling edge pulse generates when the internal drive is not latched low and the
digio.trigger[
N
].assert()
and
tsplink.trigger[
N
].assert()
functions are issued.
•
To mirror the SynchronousA trigger mode, set the pulse width to 1
μ
s or any small nonzero value.
•
Action overruns are disabled.
Figure 62: Synchronous output trigger
High-capacitance mode
Overview
The Keithley Instruments Model 2657A High Power System SourceMeter
®
instrument features a high-
capacitance mode.
Because the source-measure unit (SMU) has the ability to measure low current, issues can arise
when driving a capacitive load. The pole formed by the load capacitance and the current range
resistor can cause a phase shift in the SMU voltage control loop. This shift can lead to overshoot,
ringing, and instability. The actual operating conditions for a given capacitive load can vary. This is
due to the large, dynamic range of the instrument's current measurement capability and its wide
range of internal resistors.
Based on the type, some test applications may require capacitors larger than 100 nF. For this
purpose, you can use the high-capacitance mode to minimize overshoot, ringing and instability.
This section provides the details that you need to estimate performance based on load capacitance
and measurement conditions.
Pulse Width
Pulse Width
Output Triggers
External Drive
Internal Drive
Physical Line State
Event
Stimulus Event
Action Overrun
Summary of Contents for 2657A
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