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MAX9995
(Rev.:2011)

Dual, SiGe, High-Linearity, 1700MHz to 2700MHz Downconversion Mixer with LO Buffer/Switch

Maxim Integrated 

Dual, SiGe, High-Linearity, 1700MHz to 2700MHz

Downconversion Mixer with LO Buffer/Switch

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 VCC.

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.

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