Tektronix TDSUSB2, Руководство пользователя

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Operating Basics
Inrush Current Check
The application can perform an Inrush current check to verify that the unit under
test does not draw current higher than that specified in the USB2.0 specifications
when connected to a USB2.0 system. If the measured current drawn is higher
than a specified value, the other USB2.0 devices connected to the bus may not be
able to function properly.
When a unit is connected, there is a sharp intake of current followed by a
comparatively less steep decay. Small humps or perturbations are noticed in the
current trace, depending on when the unit reset
s .
The TDSUSB2 application automatically sets up the oscilloscope. The
application gives a direct readout of Charge (µC) and Capacitance (µF) values.
The application displays the details of the results after comparing the test results
with the USB2.0 specifications.
Figure 10: Results of the Inrush current check
Droop Measurement
The Droop voltage is the difference in the V
BUS
voltage when you apply a no load
condition and a 100 mA load to the port under test (all other ports are fully
loaded).
The Droop test evaluates the worst case droop by alternately applying a droop
load and no load to the port under test while all other ports are supplying the
maximum load possible. All the V
BUS
measurements are relative to local ground.
The TDSUSB2 application automatically sets up the oscilloscope for the
specified test configuration. When you start the application, it acquires the signal,
and provides the V
DROOP
measurement, and displays PASS or FAIL.
30 TDSUSB2 Universal Serial Bus Measurement Package