For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
General Description
The MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
are highly integrated front-end ICs that provide the lowest
cost solution for cordless phones and ISM-band radios
operating in the 900MHz band. All devices incorporate
transmit and receive image-reject mixers to reduce filter
cost. They operate with a +2.7V to +4.8V power supply,
allowing direct connection to a 3-cell battery stack.
The receive path incorporates an adjustable-gain LNA
and an image-reject downconverter with 35dB image
suppression. These features yield excellent combined
downconverter noise figure (4dB) and high linearity with
an input third-order intercept point (IP3) of up to +2dBm.
The transmitter consists of a variable-gain IF amplifier
with more than 35dB control range, an image-reject
upconverter with 35dB image rejection, and a power-
amplifier (PA) predriver that produces up to +2dBm (in
some applications serving as the final power stage).
All devices include an on-chip local oscillator (LO),
requiring only an external varactor-tuned LC tank for
operation. The integrated divide-by-64/65 dual-modulus
prescaler can also be set to a direct mode, in which it
acts as an LO buffer amplifier. Four separate power-
down inputs can be used for system power manage-
ment, including a 0.5µA shutdown mode. These parts
are compatible with commonly used modulation
schemes such as FSK, BPSK, and QPSK, as well as fre-
quency hopping and direct sequence spread-spectrum
systems. All devices come in a 28-pin SSOP package.
For applications using direct VCO or BPSK transmit mod-
ulation as well as receive image rejection, consult the
MAX2424/MAX2426 data sheet. For receive-only devices,
refer to the MAX2440/MAX2441/MAX2442 data sheet.
________________________Applications
Cordless Phones Spread-Spectrum Communications
Wireless Telemetry Two-Way Paging
Wireless Networks
Features
♦Receive/Transmit Mixers with 35dB Image Rejection
♦Adjustable-Gain LNA
♦Up to +2dBm Combined Receiver Input IP3
♦4dB Combined Receiver Noise Figure
♦>35dB of Transmit Power Control Range
♦PA Predriver Provides up to +2dBm
♦Low Current Consumption: 23mA Receive
26mA Transmit
9.5mA Oscillator
♦0.5µA Shutdown Mode
♦Operates from Single +2.7V to +4.8V Supply
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
________________________________________________________________
Maxim Integrated Products
1
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
GND
GND
GND
TANK
TXON
PREOUT
PREGND
MOD
DIV1
VCOON
RXON
CAP2
N.C.
TXIN
LNAGAIN
TXOUT
GND
GND
RXIN
TXGAIN
RXOUT
CAP1
SSOP
TOP VIEW
MAX2420
MAX2421
MAX2422
MAX2460
MAX2463
TANK
VCC
VCC
VCC
VCC
VCC
___________________Pin Configuration
19-1234; Rev 2; 2/99
PART
MAX2420EAI
MAX2421EAI
MAX2422EAI -40°C to +85°C
-40°C to +85°C
-40°C to +85°C
TEMP. RANGE PIN-PACKAGE
28 SSOP
28 SSOP
28 SSOP
_______________Ordering Information
MAX2460EAI -40°C to +85°C 28 SSOP
Functional Diagram appears on last page.
MAX2463EAI -40°C to +85°C 28 SSOP
High side
INJECTION
TYPE
fRF + 10.7
LO FREQ
(MHz)
High side
High side
fRF + 70
fRF + 46
MAX2422
MAX2421
70
46
Low side fRF - 110MAX2463 110
MAX2420
PART
10.7
IF FREQ
(MHz)
______________________Selector Guide
Low side fRF - 10.7MAX2460 10.7
EVALUATION KIT MANUAL
FOLLOWS DATA SHEET
µA
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
DC ELECTRICAL CHARACTERISTICS
(VCC = +2.7V to +4.8V, no RF signals applied, LNAGAIN = TXGAIN = open, VCOON = 2.4V, RXON = TXON = MOD = DIV1 = 0.45V,
PREGND = GND, TA= TMIN to TMAX. Typical values are at TA= +25°C, VCC = +3.3V, unless otherwise noted.)
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.
Note 1: Calculated by measuring the combined oscillator and prescaler supply current and subtracting the oscillator supply current.
Note 2: Calculated by measuring the combined oscillator and LO buffer supply current and subtracting the oscillator supply current.
Note 3: Calculated by measuring the combined receive and oscillator supply current and subtracting the oscillator supply current.
With LNAGAIN = GND, the supply current drops by 4.5mA.
Note 4: Calculated by measuring the combined transmit and oscillator supply current and subtracting the oscillator supply current.
VCC to GND...........................................................-0.3V to +5.5V
TXIN Input Power (330Ωsystem)......................................-8dBm
Voltage on TXOUT......................................-0.3V to (VCC + 1.0V)
Voltage on TXGAIN, LNAGAIN, TXON,
RXON, VCOON, DIV1, MOD ....................-0.3V to (VCC + 0.3V)
RXIN Input Power..............................................................10dBm
TANK, TANK Input Power...................................................2dBm
Continuous Power Dissipation (TA= +70°C)
SSOP (derate 9.50mW/°C above +70°C) ......................762mW
Operating Temperature Range
MAX242_EAI/MAX246_EAI................................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +165°C
Lead Temperature (soldering, 10sec).............................+300°C
PARAMETER MIN TYP MAX UNITS
Receive Supply Current (Note 3) 23 36 mA
Prescaler Supply Current
(buffer mode) (Note 2) 5.4 8.5 mA
Oscillator Supply Current
Supply-Voltage Range 2.7 4.8 V
9.5 14 mA
Prescaler Supply Current
(divide-by-64/65 mode) (Note 1) 4.2 6 mA
CONDITIONS
RXON = 2.4V, PREGND = floating
DIV1 = 2.4V
PREGND = floating
Digital Input Voltage Low 0.45 V
Transmitter Supply Current (Note 4) 26 42 mA
0.5
RXON, TXON, DIV1, VCOON, MOD
RXON = 0.45V, TXON = 2.4V, PREGND = floating
VCOON = RXON = TXON =
MOD = DIV1 = GND
Digital Input Current ±1 ±10 µAVoltage on any one digital input = VCC or GND
Digital Input Voltage High V2.4RXON, TXON, DIV1, VCOON, MOD
Shutdown Supply Current 10 µA
TA= +25°C
TA= TMIN to TMAX
LNAGAIN = 1V
AC ELECTRICAL CHARACTERISTICS
(MAX242X/246X EV kit, VCC = +3.3V; fLO = 925.7MHz (MAX2420), fLO = 961MHz (MAX2421), fLO = 985MHz (MAX2422),
fLO = 904.3MHz (MAX2460); fLO = 805MHz (MAX2463); fRXIN = 915MHz; PRXIN = -35dBm; PTXIN = -15dBm (330Ω); LNAGAIN = 2V;
TXGAIN = VCC; VCOON = 2.4V; RXON = TXON = MOD = DIV1 = PREGND = GND; TA= +25°C; unless otherwise noted.)
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
_______________________________________________________________________________________ 3
CONDITIONS UNITSMIN TYP MAXPARAMETER
MHz800 1000
Input Frequency Range
(Notes 5, 6)
MAX2421 36 46 55
MAX2420/MAX2460 8.5 10.7 12.5
MAX2463
MHz
86 110 132
IF Frequency Range
(Notes 5, 6)
20 22 24.5
MAX2422
dB26 35Image Frequency Rejection
55 70 85
LNAGAIN = VCC,
TA= +25°C 18 20 22.5
18 24
19.5 25
LNAGAIN = 1V 12
DIV1 = VCC 45
LNAGAIN = VCC,
TA= TMIN to TMAX
(Note 5)
LNAGAIN = GND
dB
-16
Conversion Power Gain (Note 7)
17 23
19 21 23.5
dB
12
Noise Figure (Notes 5, 7)
LNAGAIN = 1V dBm
-8
Input Third-Order Intercept
(Notes 5, 8) LNAGAIN = VCC -19 -17
(Note 9) ns500Receiver Turn-On Time
MHz800 1000
Output Frequency Range
(Notes 5, 6)
Receiver on or off dBm-60LO to RXIN Leakage
MAX2421 36 46 55
MAX2463
MHz
86 110 132
IF Frequency Range
MAX2420/MAX2460
MAX2422 55 70 85
dB
11 13.5 16
9 12 14.5
10 12.5 15
dB26 35Image Frequency Rejection
8.5 10.7 12.5
TA= +25°C
8 11 13.5
10 15.5
TA= TMIN to TMAX
(Note 5)
814
Conversion Gain
915
10.5 16.5
LNAGAIN = 1V dBm
-18
Input 1dB Compression LNAGAIN = VCC -26
MAX2420/MAX2421/MAX2460
MAX2422
MAX2463
MAX2420/MAX2421/MAX2460
MAX2422
MAX2463
MAX2420/2460
MAX2421
MAX2422
MAX2463
MAX2420/2460
MAX2421
MAX2422
MAX2463
LNAGAIN = VCC
LNAGAIN = 1V
RECEIVER (RXON = 2.4V)
TRANSMITTER (TXON = 2.4V)
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
4 _______________________________________________________________________________________
AC ELECTRICAL CHARACTERISTICS (continued)
(MAX242X/246X EV kit, VCC = +3.3V; fLO = 925.7MHz (MAX2420), fLO = 961MHz (MAX2421), fLO = 985MHz (MAX2422),
fLO = 904.3MHz (MAX2460); fLO = 805MHz (MAX2463); fRXIN = 915MHz; PRXIN = -35dBm; PTXIN = -15dBm (330Ω); LNAGAIN = 2V;
TXGAIN = VCC; VCOON = 2.4V; RXON = TXON = MOD = DIV1 = PREGND = GND; TA= +25°C; unless otherwise noted.)
PARAMETER MIN TYP MAX UNITS
Transmitter Turn-On Time (Note 13)
Gain Control Range (Note 12) 36
TXGAIN Control Slope (Note 12) dB
33 dB/V
400 ns
Oscillator Phase Noise
Output 1dB Compression
Oscillator Frequency Range
(Notes 5, 14)
2 dBm
690 1100 MHz
82 dBc/Hz
8
10kHz offset (Note 15)
Standby to TX, or standby to RX
CONDITIONS
1V ≤TXGAIN ≤2V
Note 5: Guaranteed by design and characterization.
Note 6: Image rejection typically falls to 30dBc at the frequency extremes.
Note 7: Refer to the
Typical Operating Characteristics
for plots showing receiver gain versus LNAGAIN voltage, input IP3 versus
LNAGAIN voltage, and noise figure versus LNAGAIN voltage.
Note 8: Two tones at PRXIN = -45dBm each, f1 = 915.0MHz and f2 = 915.2MHz.
Note 9: Time delay from RXON = 0.45V to RXON = 2.4V transition to the time the output envelope reaches 90% of its final value.
Note 10: Two tones at PTXIN = -21dBm each (330Ω), f1 = 10.6MHz, f2 = 10.8MHz (MAX2420/MAX2460), f1 = 45.9MHz,
f2 = 46.1MHz (MAX2421), f1 = 69.9MHz, f2 = 70.1MHz (MAX2422).
Note 11: Refer to the
Typical Operating Characteristics
for statistical data.
Note 12: Refer to the
Typical Operating Characteristics
for a plot showing transmitter gain versus TXGAIN voltage.
Note 13: Time delay from TXON = 0.45V to TXON = 2.4V transition to the time the output envelope reaches 90% of its final value.
Note 14: Refers to useable operating range. Tuning range of any given tank circuit design is typically much narrower (refer to Figure 2).
Note 15: Using tank components L3 = 5.0nH (Coilcraft A02T), C2 = C3 = C26 = 3.3pF, R6 = R7 = 10Ω.
Note 16: This approximates a typical application in which TXOUT is followed by an external PA and a T/R switch with finite isolation.
Note 17: Relative to the rising edge of PREOUT.
Prescaler Output Level 500 mVp-p
-11 -8
Required Modulus Setup Time
(Note 5) 10 ns
ZL= 100kΩ
| |
10pF
DIV1 = 2.4V, ZL= 50Ω, TA= +25°C
Divide-by-64/65 mode (Note 17)
Required Modulus Hold Time
(Note 5) 0 ns
Divide-by-64/65 mode (Note 17)
RX to TX with PRXIN = -45dBm (RX mode) to
PRXIN = 0dBm (TX mode) (Note 16) 70
Oscillator Buffer Output Level
(Note 5) -12 dBm
DIV1 = 2.4V, ZL= 50Ω, TA= TMIN to TMAX
Oscillator Pulling kHz
Output Third-Order Intercept
(Note 10) 11 dBm
Noise Figure 23
LO to TXOUT Suppression
(Note 11) 34 dBc
dB
OSCILLATOR AND PRESCALER
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
_______________________________________________________________________________________
5
24
28
26
34
32
30
40
38
36
42
-40 0 20-20 40 60 80 100
RECEIVER SUPPLY CURRENT
vs. TEMPERATURE
MAX2420-01
TEMPERATURE (°C)
ICC (mA)
VCC = 2.7V
RXON = VCC
PREGND = FLOATING
INCLUDES OSCILLATOR
CURRENT
VCC = 3.3V
VCC = 4.8V
26
30
28
36
34
32
44
42
40
38
46
-40 0 20-20 40 60 80 100
TRANSMITTER SUPPLY CURRENT
vs. TEMPERATURE
MAX2420-02
TEMPERATURE (°C)
ICC (mA)
VCC = 2.7V
VCC = 3.3V
VCC = 4.8V
TXON = VCC
PREGND = FLOATING
INCLUDES OSCILLATOR
CURRENT
0
1.0
0.5
2.5
2.0
1.5
4.0
3.5
3.0
4.5
-40 0 20-20 40 60 80 100
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX2420-03
TEMPERATURE (°C)
ICC (µA)
VCC = 2.7V
VCC = 3.3V
VCC = 4.8V
VCOON = GND
25
20
15
10
5
0
-5
-10
-15
-20 0 0.5 1.0 1.5 2.0
RECEIVER GAIN vs. LNAGAIN
MAX2420-04
LNAGAIN VOLTAGE (V)
RECEIVER GAIN (dB)
ADJUSTABLE
GAIN MAX
GAIN
LNA
PARTIALLY
BIASED
LNA
OFF
AVOID
THIS
REGION RXON = VCC
18
22
20
26
24
-40 0 20-20 40 60 80 100
MAX2420
RECEIVER GAIN vs. TEMPERATURE
MAX2420-07
TEMPERATURE (°C)
RECEIVER GAIN (dB)
VCC = 2.7V
VCC = 3.3V
VCC = 4.8V
LNAGAIN = VCC
RXON = VCC
-20
-15
-10
-5
0
5
0 0.5 1.0 1.5 2.0
RECEIVER INPUT IP3 vs. VLNAGAIN
MAX2420-05
LNAGAIN VOLTAGE (V)
IIP3 (dBm)
ADJUSTABLE
GAIN
AVOID
THIS
REGION
MAX
GAIN
LNA
PARTIALLY
BIASED
LNA
OFF
RXON = VCC
0
5
15
10
25
20
30
40
35
0 0.5 1.0 1.5 2.0
RECEIVER NOISE FIGURE
vs. LNAGAIN
MAX2420-06
LNAGAIN VOLTAGE (V)
NOISE FIGURE (dB)
ADJUSTABLE
GAIN
AVOID
THIS
REGION
MAX
GAIN
LNA
PARTIALLY
BIASED
LNA
OFF
DIV1 = VCC
RXON = VCC
3.0
4.0
3.5
5.0
5.5
4.5
-40 0 20-20 40 60 80 100
RECEIVER NOISE FIGURE vs.
TEMPERATURE AND SUPPLY VOLTAGE
MAX2420-08
TEMPERATURE (°C)
NOISE FIGURE (dB)
VCC = 2.7V
VCC = 3.3V
VCC = 4.8V
LNAGAIN = VCC
RXON = VCC
DIV1 = VCC
-20
-16
-18
-8
-10
-6
-12
-14
-40 0 20-20 40 60 80 100
RECEIVER INPUT IP3
vs. TEMPERATURE
MAX2420-09
TEMPERATURE (°C)
IIP3 (dBm)
LNAGAIN = 1V
LNAGAIN = 2V
RXON = VCC
Typical Operating Characteristics
(MAX242X/246X EV kit, VCC = +3.3V; fLO = 925.7MHz (MAX2420), fLO = 961MHz (MAX2421), fLO = 985MHz (MAX2422), fLO = 904.3MHz
(MAX2460); fLO = 805MHz (MAX2463); fRXIN = 915MHz; PRXIN = -35dBm; PTXIN = -15dBm (330Ω); LNAGAIN = 2V; TXGAIN = VCC;
VCOON = 2.4V; RXON = TXON = MOD = DIV1 = PREGND = GND; TA= +25°C; unless otherwise noted.)
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(MAX242X/246X EV kit, VCC = +3.3V; fLO = 925.7MHz (MAX2420), fLO = 961MHz (MAX2421), fLO = 985MHz (MAX2422), fLO = 904.3MHz
(MAX2460); fLO = 805MHz (MAX2463); fRXIN = 915MHz; PRXIN = -35dBm; PTXIN = -15dBm (330Ω); LNAGAIN = 2V; TXGAIN = VCC;
VCOON = 2.4V; RXON = TXON = MOD = DIV1 = PREGND = GND; TA= +25°C; unless otherwise noted.)
-20
10
-10
0
30
20
50
40
60
0 400 800 1200 1600 2000
RECEIVER IMAGE REJECTION
vs. RF FREQUENCY
MAX2420-11
RF FREQUENCY (MHz)
IMAGE REJECTION (dB)
RXON = VCC
-9
-8
-4
-5
-3
-6
-7
-40 0 20-20 40 60 80
MAX2420
RXOUT 1dB COMPRESSION POINT
vs. TEMPERATURE
MAX2420-10
TEMPERATURE (°C)
1dB COMPRESSION POINT (dBm)
VCC = 2.7V
VCC = 4.8V
VCC = 3.3V
RXON = VCC
60
01 100010010
RECEIVER IMAGE REJECTION
vs. IF FREQUENCY
20
10
40
30
50
MAX2420-12
IF FREQUENCY (MHz)
IMAGE REJECTION (dB)
MAX2420 MAX2460
MAX2463
MAX2422
MAX2421
RXON = VCC
2
6
4
10
8
14
16
12
18
-40 0 20-20 40 60 80 100
MAX2420
TRANSMITTER GAIN vs. TEMPERATURE
MAX2420 toc16
TEMPERATURE (°C)
TRANSMITTER GAIN (dB)
VCC = 2.7V
VCC = 4.8V
TXON = VCC
VCC = 3.3V
0
25
30
15
20
10
5
35
40
45
50
-0
-60
-40
-20
-80
-100
800600 1000 1200 1400
RXIN INPUT IMPEDANCE
vs. FREQUENCY
MAX2420 toc14
FREQUENCY (MHz)
REAL IMPEDANCE (Ω)
IMAGINARY IMPEDANCE (Ω)
REAL
IMAGINARY
RXON = VCC
-40
-30
-10
-20
10
0
20
0.5 2.01.51.0 2.5 3.0 3.5 4.54.0 5.0
TRANSMITTER GAIN
vs. TXGAIN VOLTAGE
MAX2420 toc15
TXGAIN VOLTAGE (V)
TRANSMITTER GAIN (dB)
VCC = 2.7V VCC = 4.8V
VCC = 3.3V
TXON = VCC
-90
-70
-80
-50
-60
-30
-40
-20
0
-10
10
875 895 905 915885 925 935 945 965955 975
MAX2420
TRANSMITTER OUTPUT SPECTRUM
MAX2420/21/22 toc18
FREQUENCY (MHz)
POWER (dBm)
FUNDAMENTAL
TXON = VCC
LO IMAGE
-70
-90
-80
-100
-60
-40
-50
-30
-10
-20
0
855 885865 875 895 905 925
915 935 945 955
MAX2460
TRANSMITTER OUTPUT SPECTRUM
MAX2420/21/22 toc18.1
FREQUENCY (MHz)
POWER (dBm)
TXON = VCC
IMAGE LO
FUNDAMENTAL
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
_______________________________________________________________________________________
7
-1.0
0
-0.5
1.0
0.5
2.5
2.0
1.5
3.0
-40 0-20 20 40 60 80 100
TRANSMITTER 1dB COMPRESSION POINT
vs. TEMPERATURE
MAX2420/21/22toc19
TEMPERATURE (°C)
OUTPUT 1dB COMPRESSION (dBm)
VCC = 4.8V
VCC = 3.3V
VCC = 2.7V
TXON = VCC
42
44
46
48
50
52
54
1.0 2.01.5 2.5 3.0 3.5 4.0 4.5 5.0
MAX2420
TRANSMITTER IM3 REJECTION
vs. TXGAIN VOLTAGE
MAX2420/21/22 toc20
TXGAIN VOLTAGE (V)
IM3 REJECTION
VCC = 2.7V
VCC = 3.3V
TXON = VCC
f1 = 10.6MHz
f2 = 10.8MHz
-21dBm PER TONE
VCC = 4.8V
0
20
25
15
10
5
35
30
40
45
100 900500 1300 1700 2100
TRANSMITTER IMAGE REJECTION
vs. RF FREQUENCY
MAX2420/21/22 toc21
RF FREQUENCY (MHz)
IMAGE REJECTION (dB)
TXON = VCC
50
0110 100 1000
TRANSMITTER IMAGE REJECTION
vs. IF FREQUENCY
10
5
MAX2420-22
IF FREQUENCY (MHz)
IMAGE REJECTION (dB)
20
15
30
35
25
40
45 MAX2420
MAX2463
TXON = VCC
MAX2422
MAX2421
MAX2460
4
2
0
6
10
8
12
16
14
18
24 28 30 3226 34 36 38 4240 44 46 48 50
MAX2420
TRANSMITTER LO SUPPRESSION
HISTOGRAM (n = 86)
MAX2420/21/22 toc18.5
LO SUPPRESSION (dBc)
COUNT
TXON = VCC
-70
-90
-80
-100
-60
-40
-50
-30
-10
-20
0
710 810 910 1010 1110 1210
MAX2421
TRANSMITTER OUTPUT SPECTRUM
MAX2420/21/22 toc18.2
FREQUENCY (MHz)
POWER (dBm)
TXON = VCC
IMAGE
LO
FUNDAMENTAL
550
500
01 1k 10k100 100k
PRESCALER OUTPUT LEVEL
vs. LOAD RESISTANCE
100
50
MAX2420/21/22 toc24
LOAD RESISTANCE (Ω)
PRESCALER OUTPUT LEVEL (mVp-p)
200
150
350
300
250
450
400
LOAD IS PLOTTED RESISTANCE
IN PARALLEL WITH A 10pF
OSCILLOSCOPE PROBE
(÷ 64/65 MODE)
Typical Operating Characteristics (continued)
(MAX242X/246X EV kit, VCC = + 3.3V; fLO = 925.7MHz (MAX2420), fLO = 961MHz (MAX2421), fLO = 985MHz (MAX2422), fLO = 904.3MHz
(MAX2460); fLO = 805MHz (MAX2463); fRXIN = 915MHz; PRXIN = -35dBm; PTXIN = -15dBm (330Ω); LNAGAIN = 2V; TXGAIN = VCC;
VCOON = 2.4V; RXON = TXON = MOD = DIV1 = PREGND = GND; TA= +25°C; unless otherwise noted.)
-70
-90
-80
-100
-60
-40
-50
-30
-10
-20
0
735 835 935 1035 1135 1235
MAX2422
TRANSMITTER OUTPUT SPECTRUM
MAX2420/21/22 toc18.3
FREQUENCY (MHz)
POWER (dBm)
TXON = VCC
IMAGE
LO
FUNDAMENTAL
-70
-90
-80
-100
-60
-40
-50
-30
-10
-20
0
605 655 705 1005 1055 1105
MAX2463
TRANSMITTER OUTPUT SPECTRUM
MAX2420/21/22 toc18.4
FREQUENCY (MHz)
POWER (dBm)
TXON = VCC
IMAGE LO
FUNDAMENTAL
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
8 _______________________________________________________________________________________
Pin Description
Supply Voltage Input for Receive Low-Noise Amplifier. Bypass with a 47pF low-inductance capacitor to
GND (pin 7 if possible).
6
Receiver RF Input, single-ended. The input match shown in Figure 1 maintains an input VSWR of better
than 2:1 from 902MHz to 928MHz.
5
Transmit Gain-Control Input. Connect to VCC for highest gain and best temperature stability. When
driven with a control voltage, the IF buffer gain can be adjusted over a 36dB range (see
Typical
Operating Characteristics
).
4
VCC
RXIN
TXGAIN
Prescaler/Oscillator Buffer Output. In divide-by-64/65 mode (DIV1 = low), the output level is 500mVp-p
into a high-impedance load. In divide-by-1 mode (DIV1 = high), this output delivers -8dBm into a 50Ω
load. AC couple to this pin.
21
Transmit Bias Compensation Pin. Bypass with a 47pF low-inductance capacitor and 0.01µF to GND.
Do not make any other connections to this pin.
14
No Connect. Not internally connected.13
Ground connection for the Prescaler. Tie PREGND to ground for normal operation. Leave floating to
disable the prescaler and the output buffer. Tie MOD and DIV1 to ground and leave PREOUT floating
when disabling the prescaler.
CAP2
N.C. Transmitter IF Input, 330Ω, single-ended. AC couple to this pin.12
Single-Ended, 330ΩIF Output. AC couple to this pin. 3
Receive Bias Compensation Pin. Bypass with a 47pF low-inductance capacitor and 0.01µF to GND.
Do not make any other connections to this pin.
2
Supply-Voltage Input for Master Bias Cell. Bypass with a 47pF low-inductance capacitor and 0.1µF to
GND (pin 28 if possible).
1
FUNCTIONPIN
Low-Noise Amplifier Gain-Control Input. Drive this pin high for maximum gain. When LNAGAIN is pulled
low, the LNA is capacitively bypassed and the supply current is reduced by 4.5mA. This pin can also be
driven with an analog voltage to adjust the LNA gain in intermediate states. Refer to the Receiver Gain
vs. LNAGAIN Voltage graph in the
Typical Operating Characteristics,
as well as Table 1.
10
PA Predriver Output. See Figure 1 for an example matching network, which provides better than 2:1
VSWR from 902MHz to 928MHz.
9
TXIN
LNAGAIN
TXOUT
Ground Connection for Receive Low-Noise Amplifier7 GND
RXOUT
CAP1
VCC
NAME
Ground Connection for Signal-Path Blocks, except LNA8 GND
Supply Voltage Input for Signal-Path Blocks, except LNA. Bypass with a 47pF low-inductance capacitor
and 0.01µF to GND (pin 8 if possible).
11 VCC
20
PREOUT
PREGND
Modulus Control for the Divide-by-64/65 Prescaler: high = divide-by-64, low = divide-by-65. Note that
the DIV1 pin must be at logic low when using the prescaler mode.
19
Driving VCOON with a logic high turns on the VCO, phase shifters, VCO buffers, and prescaler. The
prescaler can be selectively disabled by floating the PREGND pin.
17
Driving RXON with a logic high enables the LNA, receive mixer, and IF output buffer. VCOON must also
be high.
16
MOD
VCOON
RXON
Driving TXON with a logic high enables the transmit IF variable-gain amplifier, upconverter mixer, and PA
predriver. VCOON must also be high.
15 TXON
Driving DIV1 with a logic high disables the divide-by-64/65 prescaler and connects the PREOUT pin
directly to an oscillator buffer amplifier, which outputs -8dBm into a 50Ωload. Tie DIV1 low for divide-by-
64/65 operation. Pull this pin low when in shutdown to minimize off current.
18 DIV1
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
_______________________________________________________________________________________ 9
Pin Description (continued)
Ground Connection for VCO and Phase Shifters26 GND Ground (substrate)27 GND Ground Connection for Master Bias Cell28 GND
Supply-Voltage Input for VCO and Phase Shifters. Bypass with a 47pF low-inductance capacitor to GND
(pin 26 if possible).
23 VCC
Supply-Voltage Input for Prescaler. Bypass with a 47pF low-inductance capacitor and 0.01µF to GND
(pin 20 if possible).
22 VCC
FUNCTIONPIN NAME
Differential Oscillator Tank Port. See
Applications Information
for information on tank circuits or on using
an external oscillator.
25
Differential Oscillator Tank Port. See
Applications Information
for information on tank circuits or on using
an external oscillator.
24
TANK
TANK
VCC
VCC
VCC
17
16
15
18
19
21 1000pF
TRANSMIT IF INPUT (330Ω)
VARACTOR:
ALPHA SMV1299-004
OR EQUIVALENT
RECEIVE IF OUTPUT (330Ω)
SEE APPLICATIONS INFORMATION SECTION
L3: COILCRAFT 0805HS-060TJBC
COILCRAFT 0805HS-030TJBC
27
23
26
3
12
20
22
1
28
RECEIVE
RF INPUT
TRANSMIT
RF OUTPUT
5
9
7
6
0.01µF
0.01µF
47pF
VCC
VCC
0.1µF
VCC VCC
2
47pF0.1µF
8.2nH
12nH
22nH
18nH
47pF
47pF
47pF
8
11
0.01µF
47pF 0.01µF MAX2420
MAX2421
MAX2422
MAX2460
MAX2463
6.8
3.3
3.3
6.8
6.8
L3
(nH)
PART
VCO TANK COMPONENTS FOR
915MHz TYPICAL RF
C26
(pF) C2, C3
(pF)
1.8
3.6
3.0
1.5
2.4
3.3
4.0
4.0
4.0
4.7
R6, R7
(Ω)
10
15
15
15
15
47pF
47pF
14
0.01µF
47pF
RXIN
TXOUT
GND
VCC
VCC
GND
CAP2
GND
CAP1 VCC
VCC
TXON
RXON
VCOON
DIV1
MOD
PREOUT
TXON
RXON
VCOON
DIV1
MOD
TO PLL
GND
RXOUT
TXIN
100nH
GND
PREGND
47pF
VCC
24
25
VCO
ADJUST
C3 1k
47k
47pF
1k
C2
R6
R7
VCC
L3 C26
TANK
TXGAIN
LNAGAIN TXGAIN
LNAGAIN
10
4
MAX2420
MAX2421
MAX2422
MAX2460
MAX2463
TANK
Figure 1. Typical Operating Circuit
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
10 ______________________________________________________________________________________
Detailed Description
The following sections describe each of the functional
blocks shown in the
Functional Diagram.
Receiver
The MAX2420/MAX2421/MAX2422/MAX2460/MAX2463’s
receive path consists of a 900MHz low-noise amplifier,
an image-reject mixer, and an IF buffer amplifier.
The LNA’s gain and biasing are adjustable via the
LNAGAIN pin. Proper operation of this pin can provide
optimum performance over a wide range of signal lev-
els. The LNA can be placed in four modes by applying
a DC voltage on the LNAGAIN pin. See Table 1, as well
as the relevant
Typical Operating Characteristics
plots.
At low LNAGAIN voltages, the LNA is shut off, and the
input signal capacitively couples directly into the mixer
to provide maximum linearity for large-signal operation
(receiver close to transmitter). As the LNAGAIN voltage
is raised, the LNA begins to turn on. Between 0.5V and
1V at LNAGAIN, the LNA is partially biased and
behaves like a Class C amplifier. Avoid this operating
mode for applications where linearity is a concern. As
the LNAGAIN voltage reaches 1V, the LNA is fully
biased into Class A mode, and the gain is monotonical-
ly adjustable at LNAGAIN voltages above 1V. See the
Receiver Gain, Receiver IP3, and Receiver Noise
Figure vs. LNAGAIN plots in the
Typical Operating
Characteristics
for more information.
The downconverter is implemented using an image-
reject mixer consisting of an input buffer with two out-
puts, each of which is fed to a double-balanced mixer.
The local-oscillator (LO) port of each mixer is driven
from a quadrature LO. The LO is generated from an on-
chip oscillator and an external tank circuit. Its signal is
buffered and split into phase shifters, which provide
90° of phase shift across their outputs. This pair of LO
signals is fed to the mixers. The mixers’ outputs are
then passed through a second pair of phase shifters,
which provide a 90° phase shift across their outputs. The
resulting mixer outputs are then summed together. The
final phase relationship is such that the desired signal is
reinforced and the image signal is canceled. The down-
converter mixer output appears on the RXOUT pin, a sin-
gle-ended 330Ωoutput.
Transmitter
The transmitter operates similarly to the receiver, but
with the phase shifters at the mixer inputs. The transmit-
ter consists of an input buffer amplifier with more than
36dB of gain-adjustment range via the TXGAIN pin.
This buffer’s output is split internally into an in-phase (I)
and a quadrature-phase (Q) path. IF phase-shifting net-
works give the Q-channel path a 90° phase shift with
respect to the I channel. The I and Q signals are input
to a pair of double-balanced mixers, driven with quad-
rature LO. The mixer outputs are then summed, cancel-
ing the image component. The image-rejected output
signal is fed to the PA predriver, which outputs typically
-3dBm on the TXOUT pin.
Since the transmit and receive sections share an LO
and an IF frequency, interference will result if both sec-
tions are active at the same time.
Phase Shifters
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
devices use passive networks to provide quadrature
phase shifting for the receive IF, transmit IF, and LO
signals. Because these networks are frequency selec-
tive, proper part selection is important. Image rejection
degrades as the IF and RF move away from the
designed optimum frequencies. The MAX2420/
MAX2421/MAX2422’s phase shifters are arranged such
that the LO frequency is higher than the RF carrier fre-
quency (high-side injection), while the MAX2460/
MAX2463’s phase shifters are arranged such that the
LO frequency is lower than the RF carrier frequency
(low-side injection). Refer to the
Selector Guide
.
Local Oscillator (LO)
The on-chip LO is formed by an emitter-coupled differ-
ential pair. An external LC resonant tank sets the oscil-
lation frequency. A varactor diode is typically used to
create a voltage-controlled oscillator (VCO). See the
Applications Information
section for an example VCO
tank circuit.
The LO may be overdriven in applications where an
external signal is available. The external LO signal
should be about 0dBm from 50Ω, and should be AC
coupled into either the TANK or TANK pin. Both TANK
and TANK require pull-up resistors to VCC. See the
Applications Information
section for details.
LNA partially biased. Avoid this mode—
the LNA operates in a Class C manner
LNA capacitively bypassed, minimum
gain, maximum IP3
MODE
LNA at maximum gain (remains monotonic)
LNA gain is monotonically adjustable
1.5 < V ≤VCC
1.0 < V ≤1.5
0.5 < V < 1.0
0 < V ≤0.5
LNAGAIN
VOLTAGE (V)
Table 1. LNA Modes
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
______________________________________________________________________________________ 11
The local oscillator is resistant to LO pulling caused by
changes in load impedance that occur as the part is
switched from standby mode, with just the oscillator run-
ning to either transmit or receive mode. The amount of
LO pulling will be affected if there is power at the RXIN
port in transmit mode. The most common cause of this is
imperfect isolation in an external transmit/receive (T/R)
switch. The
AC Electrical Characteristics
table contains
specifications for this case as well.
Prescaler
The on-chip prescaler can be used in two different
modes: as a dual-modulus divide-by-64/65, or as oscil-
lator buffer amplifier. The DIV1 pin controls this func-
tion. When DIV1 is low, the prescaler is in dual-modulus
divide-by-64/65 mode; when it is high, the prescaler is
disabled and the oscillator buffer amplifier is enabled.
The buffer typically outputs -8dBm into a 50Ωload. To
minimize shutdown supply current, pull the DIV1 pin
low when in shutdown mode.
In divide-by-64/65 mode, the division ratio is controlled
by the MOD pin. When MOD is high, the prescaler is in
divide-by-64 mode; when it is low, it divides the LO fre-
quency by 65. The DIV1 pin must be at a logic low in
this mode.
To disable the prescaler entirely, leave PREGND and
PREOUT floating. Also tie the MOD and DIV1 pins to
GND. Disabling the prescaler does not affect operation
of the VCO stage.
Power Management
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463 sup-
ports four different power-management features to con-
serve battery life. The VCO section has its own control
pin (VCOON), which also serves as a master bias pin.
When VCOON is high, the LO, quadrature LO phase
shifters, and prescaler or LO buffer are all enabled. The
VCO can be powered up prior to either transmitting or
receiving, to allow it to stabilize. For transmit-to-receive
switching, the receiver and transmitter sections have
their own enable control inputs, RXON and TXON. With
VCOON high, bringing RXON high enables the receive
path, which consists of the LNA, image-reject mixers,
and IF output buffer. When this pin is low, the receive
path is inactive. The TXON input enables the IF
adjustable-gain amplifier, upconverter mixer, and PA
predriver. VCOON must be high for the transmitter to
operate. When TXON is low, the transmitter is off.
To disable all chip functions and reduce the supply
current to typically less than 0.5µA, pull VCOON, DIV1,
MOD, RXON, and TXON low.
Applications Information
Oscillator Tank
The on-chip oscillator requires a parallel-resonant tank
circuit connected across TANK and TANK. Figure 2
shows an example of an oscillator tank circuit. Inductor
L4 provides DC bias to the tank ports. Inductor L3,
capacitor C26, and the series combination of capaci-
tors C2, C3, and both halves of the varactor diode
capacitance set the resonant frequency as follows:
where CD1 is the capacitance of one varactor diode.
Choose tank components according to your application
needs, such as phase-noise requirements, tuning
range, and VCO gain. High-Q inductors such as air-
core micro springs yield low phase noise. Use a low tol-
erance inductor (L3) for predictable oscillation
frequency. Resistors R6 and R7 can be chosen from 0
to 20Ωto reduce the Q of parasitic resonance due to
series package inductance (LT). Keep R6 and R7 as
small as possible to minimize phase noise, yet large
enough to ensure oscillator start up in fundamental
mode. Oscillator start-up will be most critical with high
tuning bandwidth (low tank Q) and high temperature.
Capacitors C2 and C3 couple in the varactor. Light
C = 1
1
C2 1
C3 2
C
C26
EFF
D1
++
+
f = 1
2L3C
rEFF
π
()
()
MAX2420
MAX2421
MAX2422
MAX2460
MAX2463
LT
LT
L3 C26
L4
100nH R5
1k
R4
1kD1 = ALPHA SMV1299-004
SEE FIGURE 1 FOR R6, R7, C2, C3, C26, AND L3 COMPONENT VALUES.
1/2 D1
1/2 D1 C1
47pF
VCO_CTRL
R7
R6
C3
R8
47k
C2
VCC
Figure 2. Oscillator Tank Schematic, Using the On-Chip VCO
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
12 ______________________________________________________________________________________
coupling of the varactor is a way to reduce the effects
of high-varactor tolerance and increase loaded Q. For a
wider tuning range use larger values for C2 and C3 or a
varactor with a large capacitance ratio. Capacitor C26
is used to trim the tank oscillator frequency. Larger val-
ues for C26 will help negate the effect of stray PCB
capacitance and parasitic inductor capacitance (L3).
Choose a low-tolerance capacitor for C26.
For applications that require a wide tuning range and
low phase noise, a series coupled resonant tank may
be required as shown in Figure 4. This tank will use the
package inductance in series with inductors L1, L2,
and capacitance of varactor D1 to set the net equiva-
lent inductance which resonates in parallel with the
internal oscillator capacitance. Inductors L1 and L2
may be implemented as microstrip inductors, saving
component cost. Bias is provided to the tank port
through chokes L3 and L5. R1 and R3 should be cho-
sen large enough to de-Q the parasitic resonance due
to L3 and L5 but small enough to minimize the voltage
drop across them due to bias current. Values for R1
and R3 should be kept between 0 and 50Ω. Proper
high-frequency bypassing (C1) should be used for the
bias voltage to eliminate power supply noise from
entering the tank.
Oscillator-Tank PC Board Layout
The parasitic PC board capacitance, as well as PCB
trace inductance and package inductance, can affect
oscillation frequency, so be careful in laying out the PC
board for the oscillator tank. Keep the tank layout as
symmetrical, tightly packed, and close to the device as
possible to minimize LO feedthrough. When using a PC
board with a ground plane, a cut-out in the ground
plane (and any other planes) below the oscillator tank
will reduce parasitic capacitance.
Using an External Oscillator
If an external 50ΩLO signal source is available, it can
be used as an input to the TANK or TANK pin in place
of the on-chip oscillator (Figure 3). The oscillator signal
is AC coupled into the TANK pin and has a level of
about 0dBm from a 50Ωsource. For proper biasing of
the oscillator input stage, the TANK and TANK pins
must be pulled up to the VCC supply via 50Ωresistors.
If the application requires overdriving the internal oscil-
lator, the pull-up resistors can be increased in order to
save power. If a differential LO source such as the
MAX2620 is available, AC couple the inverting output
into TANK.
MAX2420
MAX2421
MAX2422
MAX2460
MAX2463
TANK 50Ω
50Ω
EXT LO
EXTERNAL LO LEVEL IS
0dBm FROM A 50Ω
SOURCE.
VCC
CBLOCK
0.01µF
VCC
TANK
Figure 3. Using an External Local Oscillator
MAX2420
MAX2421
MAX2422
MAX2460
MAX2463
TANK L1LT
LT L2
L3
L4
L5
R1
R2
R3
Ci
C1C2
VCC
VTUNE
TANK
Figure 4. Series Coupled Resonant Tank for Wide Tuning Range and Low Phase Noise
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
______________________________________________________________________________________ 13
Functional Diagram
RXON
TXON
CAP2
TXOUT
CAP1
RXIN
LNAGAIN 90°
90°
90°
0°
0°
Σ
Σ
MAX2420
MAX2421
MAX2422
MAX2460*
MAX2463*
PHASE
SHIFTER
÷1/64/65
BIAS
RXOUT
DIV1
MOD
PREOUT
PREGND
TANK
TANK
VCOON
TXIN
*CRISS-CROSSED PHASE-SHIFTER
CONNECTIONS
TXGAIN
90°
0°
0°
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
900MHz Image-Reject Transceivers
14 ______________________________________________________________________________________
Package Information
SSOP.EPS