Rainbow Electronics MAX2685 - Manual

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
Features
♦ 800MHz to 1000MHz RF Frequency Range
♦ +2.7V to +5.5V Single-Supply Operation
♦ Integrated LNA + Mixer + LO Buffer
♦ Logic-Controlled LNA Bypass Switch Reduces
Supply Current
♦ LNA Performance (High/Low Gain)
Gain: +15dB/-12dB
NF: 1.4dB/12dB
Input IP3: -4dBm/+16dBm
♦ Mixer Performance (High/Low Gain)
Gain: 6dB/4.6dB
NF: 13dB/12dB
Input IP3: +7dBm/-1.5dBm
♦ Supply Current
8.5mA (High Gain)
3.8mA (Low Gain)
♦ <0.1µA Supply Current in Shutdown Mode
♦ 0.8µs Receiver Enable Time
MAX2685
Low-Cost, 900MHz, Low-Noise Amplifier
and Downconverter Mixer
________________________________________________________________ Maxim Integrated Products 1
V CC
IFOUT+
IFOUT-
MAX2685
LNAIN
GAIN
LNA
LO
LNAOUT MIXIN
LNA BYPASS
LO
BUFFER
MIXER
SHDN
POWER
MANAGEMENT
GND
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
LNAOUT
GND
V CC
V CC
MIXIN
GND
GND
IFOUT+
IFOUT-
TOP VIEW
MAX2685
QSOP
LNAIN
SHDN
GAIN
GND
GND
LO
GND
Functional Diagram
19-1493; Rev 1; 12/00
PART
MAX2685EEE -40°C to +85°C
TEMP. RANGE PIN-PACKAGE
16 QSOP
EVALUATION KIT
AVAILABLE
Pin Configuration
Ordering Information
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.