MAX2685_00 Datasheet, PDF (1/10 Pages) Maxim Integrated Products – Low-Cost, 900MHz, Low-Noise Amplifier and Downconverter Mixer

19-1493; Rev 1; 12/00
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Low-Cost, 900MHz, Low-Noise Amplifier
and Downconverter Mixer
General Description
The MAX2685’s low-noise amplifier (LNA) and down-
converter mixer comprise the major blocks of an RF
front-end receiver. Optimized for 900MHz operation,
the device’s low noise figure, high gain, and high linear-
ity make it ideal for cellular, cordless, and wireless data
applications. A low supply current of 8.5mA (high-gain
mode) and 3.8mA (low-gain mode) plus a low operating
supply voltage range of +2.7V to +5.5V make it suitable
for use in 3-cell NiCd or 1-cell lithium-ion (Li+) battery
applications. A low-power shutdown mode further
extends battery life by reducing supply current below
0.1µA.
The MAX2685 includes an LNA, LNA bypass switch,
downconverter mixer, and local-oscillator (LO) buffer.
The LNA has a low noise figure of 1.4dB, a high gain of
15dB, and an input third-order intercept point (IP3) of
-4dBm. The mixer has a noise figure of 13dB, a gain of
6dB, and an input IP3 of +7dBm. In addition, an LNA
bypass switch allows two levels of gain, reducing
power consumption when high gain is not needed.
The downconverter mixer has a single-ended RF input
port and differential IF output ports. Differential opera-
tion of the IF ports offers improved even-order harmonic
rejection and increased immunity to noise. An LO buffer
allows the LO port to be driven with only -8dBm of LO
power. The MAX2685 is offered in a space-saving 16-
pin QSOP package.
Applications
Cellular/Cordless Phones 900MHz ISM-Band Radios
Wireless Data
868MHz European ISM Band
Pin Configuration
TOP VIEW
GND ¹
2
LNAIN
GND ³
GAIN ⁴
5
V_CC
SHDN ⁶
LO ⁷
GND ⁸
MAX2685
16 _LNAOUT
15
V_CC
14 _GND
13 _MIXIN
12 _GND
11 _GND
10 _IFOUT+
9 _IFOUT-
Features
o 800MHz to 1000MHz RF Frequency Range
o +2.7V to +5.5V Single-Supply Operation
o Integrated LNA + Mixer + LO Buffer
o Logic-Controlled LNA Bypass Switch Reduces
Supply Current
o LNA Performance (High/Low Gain)
Gain: +15dB/-12dB
NF: 1.4dB/12dB
Input IP3: -4dBm/+16dBm
o Mixer Performance (High/Low Gain)
Gain: 6dB/4.6dB
NF: 13dB/12dB
Input IP3: +7dBm/-1.5dBm
o Supply Current
8.5mA (High Gain)
3.8mA (Low Gain)
o <0.1µA Supply Current in Shutdown Mode
o 0.8µs Receiver Enable Time
PART
MAX2685EEE
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
16 QSOP
LNAIN
GAIN
V_CC
SHDN
GND
Functional Diagram
LNAOUT MIXIN
LNA
MIXER
LNA BYPASS
IFOUT+
IFOUT-
MAX2685
POWER
MANAGEMENT
LO
BUFFER
QSOP
LO
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.