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Figure 3. Keithley’s Series 2280S Power Supplies can characterize
small load currents with 10nA resolution and measure up to 6A very
accurately. Four load current measurement ranges—10A, 1A, 100mA,
and 10mA—allow measuring both full load currents and standby/sleep
mode currents with 6 1/2 digit resolution. It can also capture dynamic
load currents as short as 140μs.
Figure 4. As a device is powered up during characterization or production testing, the load current increases as
it cycles through the sleep, standby, and active modes. To characterize this start-up sequence, the test setup
must be capable of making fast measurements synchronized to the device’s state changes.
pulses, DMMs offer much greater
precision when making voltage
measurements. A power source, a
DMM, and an oscilloscope might be
required to make all the necessary
measurements.
A source measure unit (SMU)
instrument could be another possible
option for this application. They can
measure very low currents (down
to picoamps or less) accurately;
unfortunately, they are not typically
designed to capture narrow pulses.
Also, SMUs are generally low power
instruments and so might not have
sufficient total power to deliver the
peak current necessary to characterize
a device that draws a large amount
of peak power. In addition, because
of their extraordinary sensitivity,
SMU instruments can be relatively
expensive solutions for testing low-
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