Application Information
4-2
TSEV83102G0B - Evaluation Board User Guide
2166B–BDC–04/03
The V
PLUSD
positive supply voltage allows the adjustment of the output common mode
level from -1.05V (V
PLUSD
= -0.8V for ECL output compatibility) to +1.35V (V
PLUSD
= 1.6V
for LVDS output compatibility).
Each output voltage varies between -0.9V and -1.2V (respec1.2V and +1.5V),
leading to ±0.3V = 660 mV in differential for V
PLUSD
= -0.8V (respectively 1.6V).
4.5
ADC Gain Adjust
The ADC gain is adjustable by the means of pin R9 (pad input impedance is 1 M
Ω
in
parallel with 2 pF). A jumper denoted GAIN has been foreseen in order to have access
to the ADC gain adjust pin.
The GAIN potentiometer is dedicated to adjusting the ADC gain from approximately
0.85 up to 1.15.
The gain adjust transfer function is given below.
Figure 4-1. ADC Gain Adjust
4.6
SMA Connectors
and Microstrip
Lines De-
embedding
Fixture
Attenuation in microstrip lines can be found by taking the difference in the log magni-
tudes of the S21 scattering parameters measured on two different lengths of
meandering transmission lines.
Such a measurement also removes common losses such as those due to transitions
and connectors.
The S21 scattering parameter corresponds to the amount of power transmitted through
a two-port network.
The characteristic impedance of the microstrip meander lines must be close to 50
Ω
to
minimize impedance mismatch with the 50
Ω
network analyzer test ports.
Impedance mismatch will cause ripples in the S21 parameter as a function of both the
degree of mismatch and the length of the line.
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
-600
-400
-200
0
200
400
600
Vgain (command voltage) (mV)
ADC Gain
