Tektronix TDSUSB2, Manual

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Application Examples
Droop Test for Ports of Hub
Specifying the Equipment-Low Speed Droop Tests
The following equipment is needed to perform a Droop Test for Low Speed
device
:
Tektronix digital oscilloscope
TDSUSB2 application
TDSUSBF compliance test fixture
Two P6245or TAP1500 single-ended probes
Typical Equipment Setup-Low Speed Droop Tests
To set up the equipment for Droop test, follow these steps:
1. Use the Droop and Adjacent Trigger section for the Droop test. Use standard
USB cable to connect the loads on the test fixture to the ports of the unit
under test as shown in the following figure.
2. The setup requires two channels of the oscilloscope: one for the Droop Load
Trigger Timer that is on the Droop test load section, and the other for VBUS
that is on the Adjacent Trigger and Droop Test section of the test fixture.
Use the load switch to select appropriate loads for Droop Test.
3. In the Droop and Adjacent Trigger section on the test fixture, probe Ch1
from the VBUS and ground the pins.
4. In the Droop Test Load section on the test fixture, probe Ch2 from the
oscillator (marked OSC) and ground the pins.
5. Connect the Droop Trigger Test Load to the Port1 of the unit under test
(hub).
6. Connect the Load1 to Port2 of the hub under test.
7. Connect the Load2 to the A receptacle of the Droop and Adjacent Trigger
section on the test fixture. Connect the A pin dongle from the Droop and
Adjacent Trigger section to the Port4 of the unit under test (hub). Port4 is
the port under test of the hub.
8. Connect the Load3 to Port3 of the unit under test (hub). Now all the ports of
the unit under test are connected (hub).
82 TDSUSB2 Universal Serial Bus Measurement Package