AD6122_15 Datasheet, PDF (16/20 Pages) Analog Devices – CDMA 3 V Transmitter IF Subsystem with Integrated Voltage Regulator

AD6122
AD6122 Evaluation Board
The IF output port impedance match used during characteriza-
The AD6122 Evaluation Board consists of an AD6122, I/O con-
tion at Analog Devices is as follows:
nectors, a 20-pin dual header, 2-pin headers and four AD830
high speed video difference amplifiers. It allows the user to
AD6122
evaluate the AD6122’s IF amplifier and modulator together or
453⍀
4:1
50⍀
separately. Because the AD6122 may be used at any IF from 50
TXOPP
MHz to 350 MHz, pads are provided on the LOIPP input,
TXOP output, MODOP output and IFIP inputs to allow the
user to add matching networks. The board is configured for an
TXOPN
205⍀
453⍀
SPECTRUM
ANALYZER
IF frequency of 130.38 MHz when shipped. There is no differ-
1k⍀
ence between the configuration of the boards with the SSOP or
LPCC package.
Figure 32. IF Output Port Impedance Match Used During
Characterization at ADI
The AD830s are used to provide single-ended to differential
conversion and the appropriate phase shift for the I and Q data
input pins. As a result, a single-ended signal generator can be
used to generate these signals.
In order to test the power-down modes of the AD6122, locate
the two pin headers on the AD6122 evaluation boards labeled
E _{PD1 and PD2. By open-circuiting the pins labeled PD1, the IF}
amplifiers power down. By open-circuiting the pins labeled
PD2, the modulator powers down. Note that the IF amplifiers
and modulator are powered down unless the pins on the two pin
T _{headers, PD1 and PD2, are short circuited.}
The IF input port impedance match used during characteriza-
tion of the AD6122 at Analog Devices is as follows:
E _50⍀
L _SIGNAL
GENERATOR
1:8
383⍀
511⍀
383⍀
AD6122
IFINP
IFINN
1k⍀
O _{Figure 31. IF Input Port Impedance Match Used During}
Characterization at ADI
This is a broadband lossy match used for characterization over
S the 50 MHz to 350 MHz frequency range. All dBm references
in the characterization data collected using this match are refer-
enced to 1 kΩ. Note that the 1:8 ratio in Figure 31 is an imped-
OB ^{ance ratio and not a voltage ratio.}
This is a broadband lossy output match for the 50 MHz to
350 MHz frequency range. The 4:1 ratio in Figure 32 is an
impedance ratio and not a voltage ratio.
As shipped, the board is configured as follows:
1. J1 is open and J2 is shorted. This enables the LDO regulator.
The external PNP transistor should remain in place even
when the regulator is bypassed (the Pin LDOB is pulled up
by the transistor).
2. X11, X25, X18 and X26 are shorted and X12, X14, X19
and X21 are opened in order to connect the output of the
modulator to the input of the IF amplifiers.
3. L4 and L5, the roofing filter components are optimized for
an IF frequency of 130.38 MHz.
4. R14, R15 and R16 set the attenuation between the modula-
tor outputs and the IF amplifier inputs to 20 dB.
5. PD1 and PD2 are pulled low by the jumpers on the two pin
headers. To power down the chip, set PD1 and PD2 high by
removing the jumpers.
In order to look at the modulator and IF amplifiers separately,
disconnect the output of the modulator from the input of the IF
amplifiers. This is accomplished by short circuiting X12, X14,
X19 and X20 and open circuiting X11, X18, X25 and X26.
–16–
REV. B