Reference Droop Test
Multiple Regions
A region starts when the current rises above 100 mA and ends when the current is below 100 mA for at
least 100 μs. There may be multiple regions during the 100 ms period. The a nalysis tool calculates the
charge above 100 mA in each region. The charge of each region is listed in the report. Pass or fail is based
on the region with the largest charge.
Minimum Sample Rate
A minimum sa mple rate of 1 mega samples per second is required for proper analysis. If the sample rate
is below this value, the program still performs the analysis but will record an error indicating that the
sample rate is too low (E504).
Record Length
A record length of 100 ms or more after the first inrush event is required for the measurement. If the data
record is less than 100 ms, the result will be a failure because of insufficient measurement time.
If the oscilloscope does not have sufficient memory to capture 100 ms of data, then the inrush test will need
to be divided into 30 ms segments. Each time the inrush test is performed, the trigger should be delayed to
capture the next segment. Use USBET to analyze each inrush segment. Repeat until all segments covering
at least 100 ms of inrush data are examine d. Each and every individual inrush segment must pass. A
failure in one of the inrush segments consitutes an overall failure.
No Inrush Event Found
If there is no inrush event found, i.e. the current never rises above 100 mA, the result is considered a Pass.
However, the inrush current test should be repeated several times to ensure an accurate measurement.
Droop Test
Droop voltage is the difference between the V
BUS
value when the droop load is off and the lowest voltage
of the V
BUS
value when the droop load is powered on.
Receiver Sensitivity Test
You can test the Receiver sensitivity of a high speed device to respond to the particular data pattern
generated by the digital signal generator. Receiver Sensitivity responds whenever the data pattern level of
TDSUSB2 Universal Serial Bus Measurements Package 183
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