Teledyne LeCroy QPHY-BroadR-Reach - Manual (Page 20)

QPHY-BROADR-REACH TEST DESCRIPTIONS
For additional information about the tests supported by QPHY-BroadR-Reach please refer to the
BroadR-Reach Physical Layer Transceiver Specification For Automotive Applications, v.2.0. The
descriptions in the following tests will refer to various sections of this document.
Test 1 - Transmitter Output Droop
This test measures the transmitter output droop as specified in Section 5.4.1. This test requires that the
DUT be placed in test mode 1.
What is Measured:
The magnitude of both the positive and negative droop is measured with respect to the initial peak value
after the zero crossing and the value 500 ns after the initial peak. A passing droop value must be less
than 26.9%.
Figure 11 – Definition of Droop Measurement
Test Methodology:
The oscilloscope is set to the maximum sample rate, 200 ns/div, and to trigger on a negative edge. The
acquired signal has two bits of enhanced resolution (ERES) applied to it in order to limit the bandwidth of
the oscilloscope to a value which is suitable for this measurement. The initial peak is measured on both
the +1 (Vpk+) and -1 (Vpk-) symbols. The initial peak is determined by measuring the maximum or
minimum value on a gated portion of the waveform. The droop value is measured 500 ns from the initial
peak on both the +1 (Vdrooped+) and -1 (Vdrooped-) symbols. The droop for each symbol is calculated
by 100 x (Vdrooped/Vpk). The calculated droop values are then compared to 26.9% using pass/fail
testing.
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