MAX2043
1700MHz to 3000MHz High-Linearity,
Low LO Leakage Base-Station Rx/Tx Mixer
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part, voltage MUST be applied to V
CC
before digital
logic is applied to LOSEL.
A two-stage internal LO buffer allows a wide input
power range for the LO drive. All guaranteed specifica-
tions are for an LO signal power from -3dBm to +6dBm.
The on-chip low-loss balun along with an LO buffer dri-
ves the double-balanced mixer. All interfacing and
matching components from the LO inputs to the IF out-
puts are integrated on-chip.
High-Linearity Mixer
The core of the MAX2043 is a double-balanced, high-per-
formance passive mixer. Exceptional linearity is provided
by the large LO swing from the on-chip LO buffer.
Differential IF
The MAX2043 mixer has a DC to 350MHz IF frequency
range where the low-end frequency depends on the
frequency response of the external IF components.
Note that these differential ports are ideal for providing
enhanced IIP2 performance. Single-ended IF applica-
tions require a 1:1 balun to transform the 50Ω differen-
tial IF impedance to 50Ω single-ended system. After the
balun, the IF return loss is better than 20dB. The user
can use a differential IF amplifier on the mixer IF ports,
but a DC block is required on both IF+ and IF- ports to
keep external DC from entering the IF ports of the
mixer. The mixer requires a DC ground return on either
the RF tap pin (short tap to ground) or on each IF differ-
ential port (1kΩ resistor or an inductor from each IF dif-
ferential pin to ground).
Applications Information
Input and Output Matching
The RF and LO inputs are internally matched to 50Ω.
No matching components are required. Return loss at
the RF port is typically 17dB and return loss at the LO
ports are typically 14dB. RF and LO inputs require only
DC-blocking capacitors for interfacing.
The IF output impedance is 50Ω (differential). For eval-
uation, an external low-loss 1:1 (impedance ratio) balun
transforms this impedance to a 50Ω single-ended out-
put (see the Typical Application Circuit).
Bias Resistor
Bias current for the on-chip LO buffer is optimized by
fine-tuning the off-chip resistor on pin 17 (R1). The cur-
rent in the buffer amplifier can be reduced by raising
the value of this resistor but performance (especially IP3)
degrades. Doubling the value of this resistor reduces the
current in the device by approximately half.
Additional Tuning Components
The MAX2043 mixer performance can be further
enhanced with the use of external components. The
values of these components depend on the application
and the frequency band of interest. Consult the factory
for further details.
Layout Considerations
A properly designed PC board 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 package.
The PC board exposed pad MUST be connected to the
ground plane of the PC board. It is suggested that mul-
tiple vias be used to connect this pad to the lower-level
ground planes. This method provides a good RF/ther-
mal conduction path for the device. Solder the exposed
pad on the bottom of the device package to the PC
board. The MAX2043 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 each V
CC
pin and
TAP with the capacitors shown in the Typical
Application Circuit. See Table 1. Place the TAP bypass
capacitor to ground within 100 mils of the TAP pin.
Exposed Pad RF/Thermal Considerations
The exposed paddle (EP) of the MAX2043’s 36-pin thin
QFN-EP package provides a low thermal-resistance
path to the die. It is important that the PC board on
which the MAX2043 is mounted be designed to con-
duct heat from the EP. In addition, provide the EP with a
low-inductance path to electrical ground. The EP MUST
be soldered to a ground plane on the PC board, either
directly or through an array of plated via holes.
