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Functional Overview
GB1400 User Manual 2-29
PECL Option for GB1400 Tx
The PECL option is available for the GB1400 Tx only. The PECL option for the
GB1400 Tx is a modification that allows for an increased OFFSET RANGE for
the clock and data outputs, so that the user will be able to generate PECL levels
for testing in a PECL environment. PECL is defined as ECL operating +5.0 V
above ground.
Example:
ECL Levels PECL Levels
VOH ≈ -.9V VOH ≈ +4.1V
VOL ≈ -1.8V VOL ≈ +3.2V
VBB ≈ -1.35V VBB ≈ +3.65V
VTT ≈ -2.0V VTT ≈ +3.0V
The GB1400 front panel displays, the clock and data amplitude and offset based
on a load of 50 Ohms to ground.
The inverted output circuit is identical to the true output circuit.
In the PECL system, Vtt = +3.0V, therefore, the resulting GB1400 Tx signal will
be shifted by +1.5V. To get PECL levels at the GB1400 Tx output, set the unit
levels as follows:
Display Setting Resulting PECL Levels
(50 Ohms to +3.0V)
AMP = .90V
OFFSET = +1.7V
VOH ≈ +4.10V
VOL ≈ +3.20V