Datasheet

MAX2023
High-Dynamic-Range, Direct Up-/Downconversion
1500MHz to 2500MHz Quadrature Mod/Demod
15
Resistor R
b
provides a DC return to set the common-
mode voltage. In this case, due to the on-chip circuitry,
the voltage would be 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 might 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
tuning 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 available. The resistor values shown in the
Typical Application Circuit were chosen to provide
peak performance for the entire 1500MHz to 2300MHz
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 inductance.
For the best performance, route the ground pin traces
directly to the exposed pad under the package. The
PCB exposed pad 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 con-
duction path for the device. Solder the exposed pad on
the bottom of the device package to the PCB. The
MAX2023 evaluation kit can be used as a reference for
board layout. Gerber files are available upon request at
www.maxim-ic.com
.
Power-Supply Bypassing
Proper voltage-supply bypassing is essential for high-
frequency circuit stability. Bypass all VCC_ pins with
22pF and 0.1µF capacitors placed as close to the pins
as possible, with the smallest capacitor placed closest
to the device.
To achieve optimum performance, use good voltage-
supply layout techniques. The MAX2023 has several
RF processing stages that use the various VCC_
pins, and while they have on-chip decoupling, off-
chip interaction between them may degrade gain, lin-
earity, carrier suppression, and output power-control
range. Excessive coupling between stages may
degrade stability.
Exposed Pad RF/Thermal Considerations
The EP of the MAX2023’s 36-pin TQFN-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 pad (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 wher-
ever possible.