MAX9985ETX+ Maxim Integrated Products, MAX9985ETX+ Datasheet - Page 12

• Manufacturer Part Number: MAX9985ETX+
• Description: Up-Down Converters IC MIXER DOWN CONV DUAL
• Manufacturer: Maxim Integrated Products

Specifications of MAX9985ETX+

• Maximum Input Frequency: 1000 MHz
• Maximum Power Dissipation: 10800 mW
• Mounting Style: SMD/SMT
• Maximum Operating Frequency: 250 MHz
• Maximum Power Gain: 7.5 dB
• Operating Supply Voltage: 5 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Package / Case: TQFN-36 EP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX9985 is a dual-channel downconverter
designed to provide 6dB of conversion gain, +28.5dBm
input IP3, and +16.2dBm 1dB input compression point,
with a 10.5dB NF.
In addition to its high-linearity performance, the
MAX9985 achieves a high level of component integra-
tion. The device integrates two double-balanced active
mixers for two-channel downconversion. Both the main
and diversity channels include a balun and matching
circuitry to allow 50Ω single-ended interfaces to the RF
ports and the two LO ports. An integrated single-pole,
double-throw (SPDT) switch provides 50ns switching
time between the two LO inputs with 43dB of LO-to-LO
isolation and a -40dBm of LO leakage at the RF port.
Furthermore, the integrated LO buffers provide a high
drive level to each mixer core, reducing the LO drive
required at the MAX9985’s inputs to a -3dBm to +3dBm
range. The IF ports for both channels incorporate differ-
ential outputs for downconversion, which is ideal for
providing enhanced IIP2 performance.
Dual-channel downconversion makes the MAX9985
ideal for diversity receiver applications. In addition,
specifications are guaranteed over broad frequency
ranges to allow for use in GSM 850/950, 2G/2.5G
EDGE, WCDMA, cdma2000, and iDEN base stations.
The MAX9985 is specified to operate over a 700MHz to
1000MHz RF input range, a 570MHz to 865MHz LO
range, and a 50MHz to 250MHz IF range. The external
IF components set the lower frequency range (see the
Typical Operating Characteristics for details).
The RF input ports to both the main and diversity chan-
nels are internally matched to 50Ω, requiring no exter-
nal matching components. A DC-blocking capacitor is
required as the input is internally DC-shorted to ground
through the on-chip balun. The RF port return loss is
typically 15dB over the entire 700MHz to 1000MHz RF
frequency range.
The MAX9985 is optimized for a 570MHz to 865MHz
LO frequency range. As an added feature, the
MAX9985 includes an internal LO SPDT switch for use
in 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 typical
GSM applications. If frequency hopping is not
employed, simply set the switch to either of the LO
inputs. The switch is controlled by a digital input
Dual, SiGe, High-Linearity, 700MHz to 1000MHz
Downconversion Mixer with LO Buffer/Switch
12
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LO Inputs, Buffer, and Balun
Detailed Description
RF Port and Balun
(LOSEL), where logic-high selects LO1 and logic-low
selects LO2. LO1 and LO2 inputs are internally
matched to 50Ω, requiring only an 82pF DC-blocking
capacitor. To avoid damage to the part, voltage MUST
be applied to V
LOSEL. Alternatively, a 1kΩ resistor can be placed in
series at the LOSEL to limit the input current in applica-
tions where LOSEL is applied before V
The main and diversity channels incorporate a two-
stage LO buffer that allows for a wide-input power
range for the LO drive. All guaranteed specifications
are for an LO signal power from -3dBm to +3dBm. The
on-chip low-loss baluns, along with LO buffers, drive
the double-balanced mixers. All interfacing and match-
ing components from the LO inputs to the IF outputs
are integrated on-chip.
The core of the MAX9985 dual-channel downconverter
consists of two double-balanced, high-performance
passive mixers. Exceptional linearity is provided by the
large LO swing from the on-chip LO buffers. When com-
bined with the integrated IF amplifiers, the cascaded
IIP3, 2RF-2LO rejection, and NF performance are typi-
cally +28.5dBm, 77dBc, and 10.5dB, respectively.
The MAX9985 has a 50MHz to 250MHz 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 4:1 (impedance ratio) balun to transform
the 200Ω differential IF impedance to a 50Ω single-
ended system. After the balun, the IF return loss is bet-
ter than 20dB. The user can use a differential IF
amplifier on the mixer IF ports, but a DC block is
required on both IFD+/IFD- and IFM+/IFM- ports to keep
external DC from entering the IF ports of the mixer.
The RF and LO inputs are internally matched to 50Ω.
No matching components are required. Return loss at
the RF port is typically 15dB over the entire input range
and return loss at the LO ports are typically 25dB. 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 to a 50Ω single-ended
output (see the Typical Application Circuit ).
Applications Information
CC
before digital logic is applied to
Input and Output Matching
High-Linearity Mixer
Differential IF
CC
.