Datasheet

Maxim Integrated │ 23
MAX2022 High-Dynamic-Range, Direct Up/
Downconversion 1500MHz to 3000MHz
Quadrature Modulator/Demodulator
www.maximintegrated.com
Resistor R
b
provides a DC return to set the common-
mode voltage. In this case, due to the on-chip circuitry,
the voltage is approximately 0V DC. It can also be used
to reduce the load impedance of the next stage. Inductor
L
d
can provide a bit of high-frequency gain peaking for
wideband IF systems. Capacitor C
e
is a DC block.
Typical values for C
a
, R
a
, L
a
, and C
b
would be 1.5pF,
50Ω, 11nH, and 4.7pF, respectively. These values can
change depending on the LO, RF, and IF frequencies
used. Resistor R
b
isinthe50Ωto200Ωrange.
The circuitry presented in Figure 6 does not allow for
LO leakage at RF port nulling. Depending on the LO at
RF leakage requirement, a trim voltage may need to be
introduced on the baseband ports to null the LO leakage.
Power Scaling with Changes to the Bias
Resistors
Bias currents for the LO buffers are optimized by fine tun-
ing resistors R1, R2, and R3. Maxim recommends using
±1%-tolerance resistors; however, standard ±5% values
can be used if the ±1% components are not readily avail-
able. The resistor values shown in the Typical Application
Circuit were chosen to provide peak performance for the
entire 1500MHz to 3000MHz band. If desired, the current
can be backed off from this nominal value by choosing
different values for R1, R2, and R3. Contact the factory
for additional details.
Layout Considerations
A properly designed PCB is an essential part of any
RF/microwave circuit. Keep RF signal lines as short
as possible to reduce losses, radiation, and induc-
tance. For the best performance, route the ground pin
traces directly to the exposed pad under the pack-
age. The PCB exposed paddle MUST be connected
to the ground plane of the PCB. It is suggested that
multiple vias be used to connect this pad to the lower-
level ground planes. This method provides a good RF/
thermal conduction path for the device. Solder the
exposed pad on the bottom of the device package to
the PCB. The MAX2022 evaluation kit can be used as
areferenceforboardlayout.Gerberfilesareavailable
upon request at www.maximintegrated.com.
Power-Supply Bypassing
Proper voltage-supply bypassing is essential for high-
frequency circuit stability. Bypass all V
CC
pins with 22pF
and 0.1µF capacitors placed as close to the pins as pos-
sible. The smallest capacitor should be placed closest to
the device.
To achieve optimum performance, use good voltage-
supply layout techniques. The MAX2022 has several RF
processing stages that use the various V
CC
pins, and
while they have on-chip decoupling, off-chip interaction
between them may degrade gain, linearity, carrier sup-
pression, and output power-control range. Excessive
coupling between stages may degrade stability.
Exposed Pad RF/Thermal Considerations
The EP of the MAX2022’s 36-pin thin QFN-EP package
provides a low thermal-resistance path to the die. It is
important that the PCB on which the IC is mounted be
designed to conduct heat from this contact. In addition,
the EP provides a low-inductance RF ground path for the
device.
The exposed paddle (EP) MUST be soldered to a ground
plane on the PCB either directly or through an array of
platedviaholes.Anarrayof9 vias,ina3x3array, is
suggested. Soldering the pad to ground is critical for
efficient heat transfer. Use a solid ground plane wherever
possible.
Figure 6. Baseband Port Typical Filtering and DC Return Network
EXTERNAL
STAGE
L
a
R
a
C
b
C
c
C
d
C
a
L
b
R
b
L
c
L
d
C
e
MAX2022
I/Q OUTPUTS