MAX9994 Maxim Integrated Products, MAX9994 Datasheet - Page 9

• Manufacturer Part Number: MAX9994
• Description: 1700MHz to 2200MHz Downconversion Mixer
• Manufacturer: Maxim Integrated Products

data sheet. As an added feature, the MAX9994 includes
an internal LO SPDT switch that can be used for fre-
quency-hopping applications. The switch selects one of
the two single-ended LO ports, allowing the external
oscillator to settle on a particular frequency before it is
switched in. LO switching time is typically less than
50ns, which is more than adequate for virtually all GSM
applications. If frequency hopping is not employed, set
the switch to either of the LO inputs. The switch is con-
trolled by a digital input (LOSEL): logic-high selects
LO2, logic-low selects LO1. LO1 and LO2 inputs are
internally matched to 50Ω, requiring only a 22pF DC
blocking capacitor.
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 +3dBm.
The on-chip low-loss balun, along with an LO buffer,
drives the double-balanced mixer. All interfacing and
matching components from the LO inputs to the IF out-
puts are integrated on-chip.
The core of the MAX9994 is a double-balanced, high-
performance passive mixer. Exceptional linearity is pro-
vided by the large LO swing from the on-chip LO
buffer. When combined with the integrated IF ampli-
fiers, the cascaded IIP3, 2RF - 2LO rejection, and NF
performance is typically 26.2dBm, 67dBc, and 9.7dB,
respectively.
The MAX9994 mixer has a 40MHz to 350MHz IF fre-
quency range. The differential, open-collector IF output
ports require external pullup inductors to V
these differential outputs are ideal for providing
enhanced 2RF - 2LO rejection performance. Single-
ended IF applications require a 4:1 balun to transform
the 200Ω differential output impedance to a 50Ω single-
ended output. After the balun, the IF return loss is bet-
ter than 15dB.
The RF and LO inputs are internally matched to 50Ω.
No matching components are required. Return loss at
the RF port is typically 21dB over the entire input range
(1700MHz to 2200MHz) and return loss at the LO ports
are typically better than 14dB (1400MHz to 2000MHz).
Downconversion Mixer with LO Buffer/Switch
SiGe High-Linearity, 1700MHz to 2200MHz
Differential IF Output Amplifier
Applications Information
_______________________________________________________________________________________
Input and Output Matching
High-Linearity Mixer
CC
. Note that
RF and LO inputs require only DC-blocking capacitors
for interfacing.
The IF output impedance is 200Ω (differential). For
evaluation, an external low-loss 4:1 (impedance ratio)
balun transforms this impedance down to a 50Ω single-
ended output (see the Typical Application Circuit).
Bias currents for the LO buffer and the IF amplifier are
optimized by fine tuning resistors R1 and R2. If
reduced current is required at the expense of perfor-
mance, contact the factory for details. If the ±1% bias
resistor values are not readily available, substitute stan-
dard ±5% values.
LEXT serves to improve the LO-to-IF and RF-to-IF leak-
age. The inductance value can be adjusted by the user to
optimize the performance for a particular frequency
band. Since approximately 100mA flows through this
inductor, it is important to use a low DCR wire-wound coil.
If the LO-to-IF and RF-to-IF leakage are not critical
parameters, the inductor can be replaced by a short
circuit to ground.
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 MAX9994 Evaluation Kit can be used as a
reference for board layout. Gerber files are available
upon request at www.maxim-ic.com.
Proper voltage-supply bypassing is essential for high-
frequency circuit stability. Bypass each V
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.
Power-Supply Bypassing
Layout Considerations
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Bias Resistors
LEXT Inductor
CC
pin and
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