MAX2685
19-1493; Rev 1; 12/00
Low-Cost, 900MHz, Low-Noise Amplifier
and Downconverter Mixer
General Description Features
The MAX2685s low-noise amplifier (LNA) and down-
800MHz to 1000MHz RF Frequency Range
converter mixer comprise the major blocks of an RF
+2.7V to +5.5V Single-Supply Operation
front-end receiver. Optimized for 900MHz operation,
the devices low noise figure, high gain, and high linear-
Integrated LNA + Mixer + LO Buffer
ity make it ideal for cellular, cordless, and wireless data
Logic-Controlled LNA Bypass Switch Reduces
applications. A low supply current of 8.5mA (high-gain
mode) and 3.8mA (low-gain mode) plus a low operating Supply Current
supply voltage range of +2.7V to +5.5V make it suitable
LNA Performance (High/Low Gain)
for use in 3-cell NiCd or 1-cell lithium-ion (Li+) battery
Gain: +15dB/-12dB
applications. A low-power shutdown mode further
NF: 1.4dB/12dB
extends battery life by reducing supply current below
Input IP3: -4dBm/+16dBm
0.1A.
Mixer Performance (High/Low Gain)
The MAX2685 includes an LNA, LNA bypass switch,
Gain: 6dB/4.6dB
downconverter mixer, and local-oscillator (LO) buffer.
The LNA has a low noise figure of 1.4dB, a high gain of NF: 13dB/12dB
15dB, and an input third-order intercept point (IP3) of
Input IP3: +7dBm/-1.5dBm
-4dBm. The mixer has a noise figure of 13dB, a gain of
Supply Current
6dB, and an input IP3 of +7dBm. In addition, an LNA
8.5mA (High Gain)
bypass switch allows two levels of gain, reducing
3.8mA (Low Gain)
power consumption when high gain is not needed.
<0.1A Supply Current in Shutdown Mode
The downconverter mixer has a single-ended RF input
port and differential IF output ports. Differential opera-
0.8s Receiver Enable Time
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
Ordering Information
power. The MAX2685 is offered in a space-saving 16-
pin QSOP package.
PART TEMP. RANGE PIN-PACKAGE
Applications
MAX2685EEE -40C to +85C 16 QSOP
Cellular/Cordless Phones 900MHz ISM-Band Radios
Wireless Data 868MHz European ISM Band
Functional Diagram
Pin Configuration
LNAOUT MIXIN
TOP VIEW
LNA
1 16 MIXER
GND LNAOUT
IFOUT+
2 15
LNAIN
LNAIN V
CC
IFOUT-
3 14
GND GND
LNA BYPASS
4 13
GAIN
GAIN MIXIN
5 12
V GND
CC
MAX2685
6 11
MAX2685
SHDN GND LO
V
CC
BUFFER
7 10 POWER
LO IFOUT+ SHDN
MANAGEMENT
8 9 GND
GND IFOUT-
QSOP
LO
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxims website at www.maxim-ic.com.
EVALUATION KIT
AVAILABLELow-Cost, 900MHz, Low-Noise Amplifier
and Downconverter Mixer
ABSOLUTE MAXIMUM RATINGS
V to GND..............................................................-0.3V to +6V Continuous Power Dissipation (T = +70C)
CC A
LNAIN Input Power (50 source)...................................+10dBm 16-Pin QSOP (derate 8.3mW/C above +70C)............667mW
LO Input Power (50 source) ........................................+10dBm Junction Temperature......................................................+150C
MIXIN Input Power (50 source) ...................................+10dBm Operating Temperature Range ...........................-40C to +85C
IFOUT+, IFOUT- to GND ..........................................-0.3V to +6V Storage Temperature Range .............................-65C to +150C
LNAOUT to GND ......................................................-0.3V to +6V Lead Temperature (soldering, 10s) .................................+300C
GAIN, SHDN to GND..................................-0.3V to (V + 0.3V)
CC
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(V = +2.7V to +5.5V, V = +2V, V = +2V, LNAIN = LNAOUT = MIXIN = LO = unconnected, IFOUT+ = IFOUT- = V , T
CC SHDN GAIN CC A
= -40C to +85C. Typical values are at T = +25C and V = +3V, unless otherwise noted.)
A CC
PARAMETER CONDITIONS MIN TYP MAX UNITS
Supply Voltage Range 2.7 5.5 V
GAIN = V (Note 1) 8.5 14.1
CC
Operating Supply Current mA
GAIN = GND (Note 1) 3.8 6.4
Shutdown Supply Current 0.1 1.0 A
SHDN = GND (Note 1)
Logic Input Voltage High GAIN, SHDN 2.0 V
Logic Input Voltage Low GAIN, SHDN 0.5 V
Logic Input Current V = V = 0 to 5.5V (Note 1) 0.01 1 A
SHDN GAIN
AC ELECTRICAL CHARACTERISTICS
(MAX2685 EV kit, V = V = +3V, f = f = 880MHz, f = 960MHz, P = -30dBm, P = -8dBm, P = -25dBm,
CC SHDN LNAIN MIXIN LO LNAIN LO MIXIN
differential IFOUT operation, Z = 50 , T = +25C, unless otherwise noted.)
o A
PARAMETER CONDITIONS MIN TYP MAX UNITS
LOW-NOISE AMPLIFIER (LNA)
RF Frequency Range (Note 2) 800 1000 MHz
GAIN = V (Note 1) 13 15 16.2
CC
LNA Gain dB
GAIN = GND (Note 1) -14 -12 -10.3
LNA Gain Variation over Temperature GAIN = V , T = T to T (Note 3) 0.9 1.6 dB
CC A MIN MAX
GAIN = V 1.4
CC
LNA Noise Figure dB
GAIN = GND 12.2
GAIN = V (Note 4) -4.1
CC
LNA Input IP3 dBm
GAIN = GND (Note 5) +16.2
LNA Input 1dB Compression GAIN = V -18.4 dBm
CC
GAIN = V -18.6
CC
LNAOUT Port Return Loss dB
GAIN = GND -11.3
DOWNCONVERTER MIXER
RF Frequency Range (Note 2) 800 1000 MHz
GAIN = V (Note 1) 4.7 6.1 7.0
CC
Mixer Conversion Gain dB
GAIN = GND (Note 1) 2.5 4.6 6.0
2 _______________________________________________________________________________________
MAX2685