MAX9995
Dual, SiGe, High-Linearity, 1700MHz to 2700MHz
Downconversion Mixer with LO Buffer/Switch
10
Maxim Integrated
Detailed Description
The MAX9995 dual, high-linearity, downconversion
mixer provides 6.1dB gain and +25.6dBm IIP3, with a
9.8dB noise figure. Integrated baluns and matching cir-
cuitry allow 50Ω single-ended interfaces to the RF and
LO ports. A single-pole, double-throw (SPDT) LO
switch provides 50ns switching time between LO
inputs, with 50dB LO-to-LO isolation. Furthermore, the
integrated LO buffer provides a high drive level to the
mixer core, reducing the LO drive required at the
MAX9995’s inputs to -3dBm. The IF port incorporates a
differential output, which is ideal for providing
enhanced 2RF - 2LO performance.
Specifications are guaranteed over broad frequency
ranges to allow for use in WCDMA, TD-SCDMA, LTE,
TD-LTE, and GSM/EDGE base stations. The MAX9995
is specified to operate over an RF input range of
1700MHz to 2700MHz, an LO range of 1400MHz to
2600MHz, and an IF range of 40MHz to 350MHz.
Operation beyond this is possible; however, perfor-
mance is not characterized. This device is available in
a compact 6mm x 6mm, 36-pin TQFN package with an
exposed pad.
RF Input and Balun
The MAX9995’s two RF inputs (RFMAIN and RFDIV) are
internally matched to 50Ω, requiring no external match-
ing components. DC-blocking capacitors are required
as the inputs are internally DC shorted to ground
through the on-chip baluns. Input return loss is typically
14dB over the entire RF frequency range of 1700MHz
to 2700MHz.
LO Input, Switch, Buffer, and Balun
The mixers can be used for either high-side or low-side
injection applications with an LO frequency range of
1400MHz to 2600MHz. As an added feature, the
MAX9995 includes an internal LO SPDT switch that can
be used for frequency-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 controlled by a digital input
(LOSEL): logic-high selects LO1, and logic-low selects
LO2. 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.
High-Linearity Mixers
The core of the MAX9995 is a pair of double-balanced,
high-performance passive mixers. Exceptional linearity
is provided 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 +25.6dBm, 66dBc, and 9.8dB,
respectively.
Differential IF Output Amplifiers
The MAX9995 mixers have an IF frequency range of
40MHz to 350MHz. The differential, open-collector IF
output ports require external pullup inductors to V
CC
.
Note that these differential outputs are ideal for provid-
ing 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, VSWR is typically 1.5:1.
Applications Information
Input and Output Matching
The RF and LO inputs are internally matched to 50Ω.
No matching components are required. Return loss at
each RF port is typically 14dB over the entire input
range (1700MHz to 2700MHz), and return loss at the
LO ports is typically 18dB (1400MHz to 2000MHz). 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 Resistors
Bias currents for the LO buffer and the IF amplifier are
optimized by fine tuning the resistors (R1, R2, R4, and
R5). If reduced current is required at the expense of per-
formance, contact the factory. If the ±1% bias resistor
values are not readily available, substitute standard ±5%
values.
