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19-1234; Rev 2; 2/99
L MANUA ION KIT ALUAT DATA SHEET EV WS FOLLO
900MHz Image-Reject Transceivers
Features
o Receive/Transmit Mixers with 35dB Image Rejection o Adjustable-Gain LNA o Up to +2dBm Combined Receiver Input IP3 o 4dB Combined Receiver Noise Figure o >35dB of Transmit Power Control Range o PA Predriver Provides up to +2dBm o Low Current Consumption: 23mA Receive 26mA Transmit 9.5mA Oscillator o 0.5A Shutdown Mode o Operates from Single +2.7V to +4.8V Supply
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 poweramplifier (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 powerdown inputs can be used for system power management, including a 0.5A shutdown mode. These parts are compatible with commonly used modulation schemes such as FSK, BPSK, and QPSK, as well as frequency hopping and direct sequence spread-spectrum systems. All devices come in a 28-pin SSOP package. For applications using direct VCO or BPSK transmit modulation as well as receive image rejection, consult the MAX2424/MAX2426 data sheet. For receive-only devices, refer to the MAX2440/MAX2441/MAX2442 data sheet.
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
_______________Ordering Information
PART MAX2420EAI MAX2421EAI MAX2422EAI MAX2460EAI MAX2463EAI TEMP. RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 28 SSOP 28 SSOP 28 SSOP 28 SSOP 28 SSOP
Functional Diagram appears on last page.
___________________Pin Configuration
TOP VIEW
VCC 1 CAP1 2 RXOUT 3 TXGAIN 4 RXIN 5 VCC 6 GND 7 GND 8 TXOUT 9 LNAGAIN 10 VCC 11 TXIN 12 N.C. 13 CAP2 14 28 GND 27 GND 26 GND 25 TANK
________________________Applications
Cordless Phones Wireless Telemetry Wireless Networks Spread-Spectrum Communications Two-Way Paging
______________________Selector Guide
PART MAX2420 MAX2421 MAX2422 MAX2460 MAX2463 IF FREQ (MHz) 10.7 46 70 10.7 110 INJECTION TYPE High side High side High side Low side Low side LO FREQ (MHz) fRF + 10.7 fRF + 46 fRF + 70 fRF - 10.7 fRF - 110
MAX2420 MAX2421 MAX2422 MAX2460 MAX2463
24 TANK 23 VCC 22 VCC 21 PREOUT 20 PREGND 19 MOD 18 DIV1 17 VCOON 16 RXON 15 TXON
SSOP 1
________________________________________________________________ Maxim Integrated Products
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.
900MHz Image-Reject Transceivers MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
ABSOLUTE MAXIMUM RATINGS
VCC to GND ...........................................................-0.3V to +5.5V TXIN Input Power (330 system) ......................................-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 = +70C) SSOP (derate 9.50mW/C above +70C) ......................762mW Operating Temperature Range MAX242_EAI/MAX246_EAI ................................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +165C Lead Temperature (soldering, 10sec) .............................+300C
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
(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 = +25C, VCC = +3.3V, unless otherwise noted.) PARAMETER Supply-Voltage Range Oscillator Supply Current Prescaler Supply Current (divide-by-64/65 mode) (Note 1) Prescaler Supply Current (buffer mode) (Note 2) Receive Supply Current (Note 3) Transmitter Supply Current (Note 4) Shutdown Supply Current Digital Input Voltage High Digital Input Voltage Low Digital Input Current DIV1 = 2.4V RXON = 2.4V, PREGND = floating RXON = 0.45V, TXON = 2.4V, PREGND = floating VCOON = RXON = TXON = MOD = DIV1 = GND TA = +25C TA = TMIN to TMAX 2.4 0.45 1 10 PREGND = floating CONDITIONS MIN 2.7 9.5 4.2 5.4 23 26 0.5 10 TYP MAX 4.8 14 6 8.5 36 42 UNITS V mA mA mA mA mA A A V V A
RXON, TXON, DIV1, VCOON, MOD RXON, TXON, DIV1, VCOON, MOD Voltage on any one digital input = VCC or GND
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.
2
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900MHz Image-Reject Transceivers
AC ELECTRICAL CHARACTERISTICS
(MAX242X/246X EV kit, V CC = +3.3V; f LO = 925.7MHz (MAX2420), f LO = 961MHz (MAX2421), f LO = 985MHz (MAX2422), fLO = 904.3MHz (MAX2460); fLO = 805MHz (MAX2463); fRXIN = 915MHz; PRXIN = -35dBm; PTXIN = -15dBm (330); LNAGAIN = 2V; TXGAIN = VCC; VCOON = 2.4V; RXON = TXON = MOD = DIV1 = PREGND = GND; TA = +25C; unless otherwise noted.) PARAMETER RECEIVER (RXON = 2.4V) Input Frequency Range (Notes 5, 6) MAX2420/MAX2460 IF Frequency Range (Notes 5, 6) Image Frequency Rejection MAX2420/MAX2421/MAX2460 LNAGAIN = VCC, TA = +25C Conversion Power Gain (Note 7) MAX2422 MAX2463 MAX2420/MAX2421/MAX2460 MAX2421 MAX2422 MAX2463 800 8.5 36 55 86 26 20 19 18 19.5 18 17 12 -16 LNAGAIN = VCC LNAGAIN = 1V -19 4 12 -17 -8 -26 -18 -60 500 5 dB dBm dBm dBm ns 10.7 46 70 110 35 22 21 20 24.5 23.5 22.5 25 24 23 dB 1000 12.5 55 85 132 dB MHz MHz CONDITIONS MIN TYP MAX UNITS
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
LNAGAIN = VCC, TA = TMIN to TMAX MAX2422 (Note 5) MAX2463 LNAGAIN = 1V LNAGAIN = GND
Noise Figure (Notes 5, 7) Input Third-Order Intercept (Notes 5, 8) Input 1dB Compression LO to RXIN Leakage Receiver Turn-On Time TRANSMITTER (TXON = 2.4V) Output Frequency Range (Notes 5, 6)
DIV1 = VCC LNAGAIN = 1V LNAGAIN = VCC LNAGAIN = 1V LNAGAIN = VCC LNAGAIN = 1V Receiver on or off (Note 9)
800 MAX2420/MAX2460 8.5 36 55 86 26 MAX2420/2460 TA = +25C MAX2421 MAX2422 MAX2463 MAX2420/2460 TA = TMIN to TMAX MAX2421 (Note 5) MAX2422 MAX2463 11 10 9 8 10.5 10 9 8 10.7 46 70 110 35 13.5 12.5 12 11
1000 12.5 55 85 132
MHz
IF Frequency Range
MAX2421 MAX2422 MAX2463
MHz
Image Frequency Rejection
dB 16 15 14.5 13.5 16.5 15.5 15 14 3 dB
Conversion Gain
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900MHz Image-Reject Transceivers MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
AC ELECTRICAL CHARACTERISTICS (continued)
(MAX242X/246X EV kit, V CC = +3.3V; f LO = 925.7MHz (MAX2420), f LO = 961MHz (MAX2421), f LO = 985MHz (MAX2422), fLO = 904.3MHz (MAX2460); fLO = 805MHz (MAX2463); fRXIN = 915MHz; PRXIN = -35dBm; PTXIN = -15dBm (330); LNAGAIN = 2V; TXGAIN = VCC; VCOON = 2.4V; RXON = TXON = MOD = DIV1 = PREGND = GND; TA = +25C; unless otherwise noted.) PARAMETER Output 1dB Compression Output Third-Order Intercept (Note 10) LO to TXOUT Suppression (Note 11) Noise Figure TXGAIN Control Slope (Note 12) Gain Control Range (Note 12) Transmitter Turn-On Time (Note 13) OSCILLATOR AND PRESCALER Oscillator Frequency Range (Notes 5, 14) Oscillator Phase Noise Oscillator Pulling Prescaler Output Level Oscillator Buffer Output Level (Note 5) Required Modulus Setup Time (Note 5) Required Modulus Hold Time (Note 5) 10kHz offset (Note 15) Standby to TX, or standby to RX RX to TX with PRXIN = -45dBm (RX mode) to PRXIN = 0dBm (TX mode) (Note 16) ZL = 100k | | 10pF DIV1 = 2.4V, ZL = 50, TA = +25C DIV1 = 2.4V, ZL = 50, TA = TMIN to TMAX Divide-by-64/65 mode (Note 17) Divide-by-64/65 mode (Note 17) -11 -12 10 0 690 82 8 70 500 -8 kHz mVp-p dBm ns ns 1100 MHz dBc/Hz 1V TXGAIN 2V CONDITIONS MIN TYP 2 11 34 23 33 36 400 MAX UNITS dBm dBm dBc dB dB/V dB ns
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 (330), 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 = 10. 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.
4
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900MHz Image-Reject Transceivers
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 (330); LNAGAIN = 2V; TXGAIN = VCC; VCOON = 2.4V; RXON = TXON = MOD = DIV1 = PREGND = GND; TA = +25C; unless otherwise noted.)
RECEIVER SUPPLY CURRENT vs. TEMPERATURE
MAX2420-01
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
TRANSMITTER SUPPLY CURRENT vs. TEMPERATURE
MAX2420-02
SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
4.0 3.5 VCOON = GND
MAX2420-03
42 40 38 36 ICC (mA) 34 32 30 28 26 24 -40 -20 0 20 40 60 80 RXON = VCC PREGND = FLOATING INCLUDES OSCILLATOR CURRENT VCC = 4.8V
46 44 42 40 ICC (mA) 38 36 34 32 30 28 26 -40 -20 0 20 VCC = 3.3V VCC = 2.7V TXON = VCC PREGND = FLOATING INCLUDES OSCILLATOR CURRENT 40 60 80 VCC = 4.8V
4.5
3.0 ICC (A) 2.5 2.0 1.5 1.0 0.5 0 100 -40 -20 0 20 40 60 80 100 VCC = 2.7V VCC = 4.8V VCC = 3.3V
VCC = 3.3V VCC = 2.7V
100
TEMPERATURE (C)
TEMPERATURE (C)
TEMPERATURE (C)
RECEIVER GAIN vs. LNAGAIN
MAX2420-04
RECEIVER INPUT IP3 vs. VLNAGAIN
MAX2420-05
RECEIVER NOISE FIGURE vs. LNAGAIN
35 30 NOISE FIGURE (dB) 25 20 15 10 5 AVOID THIS REGION 0 0.5 1.0 DIV1 = VCC RXON = VCC LNA ADJUSTABLE MAX PARTIALLY GAIN GAIN BIASED
MAX2420-06
25 20 15 RECEIVER GAIN (dB) 10 5 0 -5 -10 -15 -20 0 LNA OFF
LNA PARTIALLY BIASED
5 LNA OFF LNA ADJUSTABLE MAX PARTIALLY GAIN GAIN BIASED AVOID THIS REGION
40 LNA OFF
0
ADJUSTABLE GAIN
MAX GAIN
IIP3 (dBm)
-5
-10
AVOID THIS REGION RXON = VCC
-15 RXON = VCC
-20 0.5 1.0 1.5 2.0 0 0.5 1.0 LNAGAIN VOLTAGE (V)
0 1.5 2.0 1.5 2.0 LNAGAIN VOLTAGE (V) LNAGAIN VOLTAGE (V)
MAX2420 RECEIVER GAIN vs. TEMPERATURE
MAX2420-07
RECEIVER NOISE FIGURE vs. TEMPERATURE AND SUPPLY VOLTAGE
MAX2420-08
RECEIVER INPUT IP3 vs. TEMPERATURE
MAX2420-09
26 RECEIVER GAIN (dB)
LNAGAIN = VCC RXON = VCC VCC = 2.7V VCC = 4.8V
5.5 LNAGAIN = VCC RXON = VCC DIV1 = VCC VCC = 4.8V VCC = 3.3V 4.0 VCC = 2.7V 3.5
-6 -8 -10 IIP3 (dBm) LNAGAIN = 1V
5.0 NOISE FIGURE (dB) 24 22 VCC = 3.3V
4.5
-12 -14 -16 -18 RXON = VCC
20
LNAGAIN = 2V
18 3.0 -40 -20 0 20 40 60 80 100 -40 -20 0 20 40 60 80 100 TEMPERATURE (C) TEMPERATURE (C)
-20 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
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5
900MHz Image-Reject Transceivers MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
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 (330); LNAGAIN = 2V; TXGAIN = VCC; VCOON = 2.4V; RXON = TXON = MOD = DIV1 = PREGND = GND; TA = +25C; unless otherwise noted.)
MAX2420 RXOUT 1dB COMPRESSION POINT vs. TEMPERATURE
MAX2420-10
RECEIVER IMAGE REJECTION vs. RF FREQUENCY
MAX2420-11
RECEIVER IMAGE REJECTION vs. IF FREQUENCY
MAX2420 50 IMAGE REJECTION (dB) 40 30 20 10 0 MAX2460 RXON = VCC
MAX2420-12 MAX2420/21/22 toc18.1 MAX2420 toc16
-3 RXON = VCC 1dB COMPRESSION POINT (dBm) -4 VCC = 4.8V -5 -6 -7 -8 -9 -40 -20 0 20 40 60 80 TEMPERATURE (C) VCC = 2.7V VCC = 3.3V
60 RXON = VCC 50 IMAGE REJECTION (dB) 40 30 20 10 0 -10 -20 0 400 800 1200 1600
60
MAX2422 MAX2421 MAX2463
2000
1
10
100
1000
RF FREQUENCY (MHz)
IF FREQUENCY (MHz)
RXIN INPUT IMPEDANCE vs. FREQUENCY
50 45 40 REAL IMPEDANCE () 35 30 25 20 15 10 5 0 600 800 1000 1200 1400 FREQUENCY (MHz) -0 -40 0.5 -20 REAL -40 IMAGINARY
MAX2420 toc14
TRANSMITTER GAIN vs. TXGAIN VOLTAGE
MAX2420 toc15
MAX2420 TRANSMITTER GAIN vs. TEMPERATURE
18 16 TRANSMITTER GAIN (dB) 14 12 10 8 6 4 TXON = VCC 2 -40 -20 0 20 40 60 80 100 VCC = 2.7V VCC = 3.3V VCC = 4.8V
-100
20 10 TRANSMITTER GAIN (dB) VCC = 3.3V 0 -10 -20 -30 TXON = VCC 1.0 1.5 2.0 VCC = 2.7V VCC = 4.8V
RXON = VCC IMAGINARY IMPEDANCE () -80
-60
2.5 3.0 3.5 4.0 4.5 5.0
TXGAIN VOLTAGE (V)
TEMPERATURE (C)
TXOUT OUTPUT IMPEDANCE vs. FREQUENCY
MAX2420toc17
MAX2420 TRANSMITTER OUTPUT SPECTRUM
0 -10 -20 POWER (dBm) -30 -40 -50 -60 -70 LO IMAGE TXON = VCC FUNDAMENTAL
MAX2420/21/22 toc18
MAX2460 TRANSMITTER OUTPUT SPECTRUM
0 -10 -20 -30 POWER (dBm) -40 -50 -60 -70 -80 -90 -100 IMAGE LO TXON = VCC FUNDAMENTAL
150 REAL OR IMAGINARY IMPEDANCE () 100 50 0 -50 -100 -150 -200 -250 -300 TXON = VCC IMAGINARY REAL
10
-80 -90 875 885 895 905 915 925 935 945 955 965 975 FREQUENCY (MHz)
600 800 1000 1200 1400 1600 1800 2000 FREQUENCY (MHz)
855 865 875 885 895 905 915 925 935 945 955 FREQUENCY (MHz)
6
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900MHz Image-Reject Transceivers
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 (330); LNAGAIN = 2V; TXGAIN = VCC; VCOON = 2.4V; RXON = TXON = MOD = DIV1 = PREGND = GND; TA = +25C; unless otherwise noted.)
MAX2421 TRANSMITTER OUTPUT SPECTRUM
MAX2420/21/22 toc18.2
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
MAX2422 TRANSMITTER OUTPUT SPECTRUM
MAX2420/21/22 toc18.3
MAX2463 TRANSMITTER OUTPUT SPECTRUM
-10 -20 -30 POWER (dBm) -40 -50 -60 -70 -80 -90 -100 IMAGE LO TXON = VCC FUNDAMENTAL
MAX2420/21/22 toc18.4
0 -10 -20 -30 POWER (dBm) -40 -50 -60 -70 -80 -90 -100 710 810 910 1010 1110 TXON = VCC FUNDAMENTAL LO IMAGE
0 -10 -20 -30 POWER (dBm) -40 -50 -60 -70 -80 -90 -100 LO IMAGE TXON = VCC FUNDAMENTAL
0
1210
735
835
935
1035
1135
1235
605
655
705
1005
1055
1105
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
MAX2420 TRANSMITTER LO SUPPRESSION HISTOGRAM (n = 86)
MAX2420/21/22 toc18.5
TRANSMITTER 1dB COMPRESSION POINT vs. TEMPERATURE
MAX2420/21/22toc19
MAX2420 TRANSMITTER IM3 REJECTION vs. TXGAIN VOLTAGE
TXON = VCC f1 = 10.6MHz f2 = 10.8MHz -21dBm PER TONE
MAX2420/21/22 toc20
18 16 14 12 COUNT 10 8 6 4 2 0 24 26 28 30 32 34 36 38 40 42 44 46 48 50 LO SUPPRESSION (dBc) TXON = VCC
3.0 TXON = VCC OUTPUT 1dB COMPRESSION (dBm) 2.5 2.0 1.5 1.0 0.5 0 -0.5 -1.0 -40 -20 0 20 40 60 80 VCC = 2.7V VCC = 4.8V
54 52 IM3 REJECTION 50 48 46 44 VCC = 2.7V 42 VCC = 3.3V VCC = 4.8V
VCC = 3.3V
100
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
TEMPERATURE (C)
TXGAIN VOLTAGE (V)
TRANSMITTER IMAGE REJECTION vs. RF FREQUENCY
MAX2420/21/22 toc21
TRANSMITTER IMAGE REJECTION vs. IF FREQUENCY
MAX2420-22
PRESCALER OUTPUT LEVEL vs. LOAD RESISTANCE
PRESCALER OUTPUT LEVEL (mVp-p) 500 450 400 350 300 250 200 150 100 50 0 LOAD IS PLOTTED RESISTANCE IN PARALLEL WITH A 10pF OSCILLOSCOPE PROBE (/ 64/65 MODE) 1 100 1k 10k 100k
MAX2420/21/22 toc24
45 40 IMAGE REJECTION (dB) 35 30 25 20 15 10 5 0 100 500 900 1300 1700 TXON = VCC
50 45 40 IMAGE REJECTION (dB) 35 30 25 20 15 10 5 0 TXON = VCC 1 10 100 MAX2460 MAX2420 MAX2421 MAX2422 MAX2463
550
2100
1000
RF FREQUENCY (MHz)
IF FREQUENCY (MHz)
LOAD RESISTANCE ()
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7
900MHz Image-Reject Transceivers MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
Pin Description
PIN 1 2 3 4 NAME VCC CAP1 RXOUT TXGAIN FUNCTION Supply-Voltage Input for Master Bias Cell. Bypass with a 47pF low-inductance capacitor and 0.1F to GND (pin 28 if possible). Receive Bias Compensation Pin. Bypass with a 47pF low-inductance capacitor and 0.01F to GND. Do not make any other connections to this pin. Single-Ended, 330 IF Output. AC couple to this pin. 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). 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. Supply Voltage Input for Receive Low-Noise Amplifier. Bypass with a 47pF low-inductance capacitor to GND (pin 7 if possible). Ground Connection for Receive Low-Noise Amplifier Ground Connection for Signal-Path Blocks, except LNA PA Predriver Output. See Figure 1 for an example matching network, which provides better than 2:1 VSWR from 902MHz to 928MHz. 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. Supply Voltage Input for Signal-Path Blocks, except LNA. Bypass with a 47pF low-inductance capacitor and 0.01F to GND (pin 8 if possible). Transmitter IF Input, 330, single-ended. AC couple to this pin. No Connect. Not internally connected. Transmit Bias Compensation Pin. Bypass with a 47pF low-inductance capacitor and 0.01F to GND. Do not make any other connections to this pin. Driving TXON with a logic high enables the transmit IF variable-gain amplifier, upconverter mixer, and PA predriver. VCOON must also be high. Driving RXON with a logic high enables the LNA, receive mixer, and IF output buffer. VCOON must also be high. 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. 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 50 load. Tie DIV1 low for divide-by64/65 operation. Pull this pin low when in shutdown to minimize off current. 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. 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. 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 50 load. AC couple to this pin.
5 6 7 8 9
RXIN VCC GND GND TXOUT
10
LNAGAIN
11 12 13 14 15 16 17
VCC TXIN N.C. CAP2 TXON RXON VCOON
18
DIV1
19
MOD
20
PREGND
21
PREOUT
8
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900MHz Image-Reject Transceivers
Pin Description (continued)
PIN 22 23 24 25 26 27 28 NAME VCC VCC TANK TANK GND GND GND FUNCTION Supply-Voltage Input for Prescaler. Bypass with a 47pF low-inductance capacitor and 0.01F to GND (pin 20 if possible). Supply-Voltage Input for VCO and Phase Shifters. Bypass with a 47pF low-inductance capacitor to GND (pin 26 if possible). Differential Oscillator Tank Port. See Applications Information for information on tank circuits or on using an external oscillator. Differential Oscillator Tank Port. See Applications Information for information on tank circuits or on using an external oscillator. Ground Connection for VCO and Phase Shifters Ground (substrate) Ground Connection for Master Bias Cell
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
VCC 1 0.1F 47pF 28 2 0.1F RECEIVE RF INPUT 47pF GND 8.2nH VCC 12nH 47pF TRANSMIT RF OUTPUT 22nH 47pF 9 18nH 47pF VCC 11 0.01F 47pF 8 14 0.01F 47pF 4 10 47pF GND 1000pF CAP2 PREOUT MOD DIV1 VCOON RXON TXON 21 19 18 17 16 15 VCC 24 TANK R6 6 7 TXOUT VCC GND TANK 25 GND 5 RXIN GND CAP1 PREGND VCC VCC VCC 22
VCC
VCO TANK COMPONENTS FOR 915MHz TYPICAL RF 0.01F PART MAX2420 MAX2421 MAX2422 L3 (nH) 6.8 3.3 3.3 6.8 6.8 C26 (pF) 1.8 3.6 3.0 1.5 2.4 C2, C3 R6, R7 () (pF) 3.3 4.0 4.0 4.0 4.7 10 15 15 15 15
47pF 20 VCC 23 47pF 26 27 3 0.01F TXIN 12 0.01F
MAX2460 MAX2463
MAX2420 MAX2421 MAX2422 MAX2460 MAX2463
SEE APPLICATIONS INFORMATION SECTION L3: COILCRAFT 0805HS-060TJBC COILCRAFT 0805HS-030TJBC RECEIVE IF OUTPUT (330)
RXOUT
TRANSMIT IF INPUT (330) VCC
VARACTOR: ALPHA SMV1299-004 OR EQUIVALENT R7
100nH 1k C2 47k
L3
C26
VCO ADJUST 47pF
C3 TO PLL MOD DIV1 VCOON RXON TXON
1k
TXGAIN LNAGAIN
TXGAIN LNAGAIN
Figure 1. Typical Operating Circuit
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900MHz Image-Reject Transceivers MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
Detailed Description
The following sections describe each of the functional blocks shown in the Functional Diagram. 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 downconverter mixer output appears on the RXOUT pin, a single-ended 330 output.
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 levels. 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 monotonically 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 imagereject mixer consisting of an input buffer with two outputs, 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 onchip 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
Transmitter
The transmitter operates similarly to the receiver, but with the phase shifters at the mixer inputs. The transmitter 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 networks 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 quadrature LO. The mixer outputs are then summed, canceling 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 sections 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 selective, 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 frequency (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 differential pair. An external LC resonant tank sets the oscillation 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 50, and should be AC coupled into either the TANK or TANK pin. Both TANK and TANK require pull-up resistors to V CC. See the Applications Information section for details.
Table 1. LNA Modes
LNAGAIN VOLTAGE (V) 0 < V 0.5 0.5 < V < 1.0 1.0 < V 1.5 1.5 < V VCC MODE LNA capacitively bypassed, minimum gain, maximum IP3 LNA partially biased. Avoid this mode-- the LNA operates in a Class C manner LNA gain is monotonically adjustable LNA at maximum gain (remains monotonic)
10
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900MHz Image-Reject Transceivers
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 running 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.
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 capacitors C2, C3, and both halves of the varactor diode capacitance set the resonant frequency as follows: 1 fr = 2 L3 CEFF
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
Prescaler
The on-chip prescaler can be used in two different modes: as a dual-modulus divide-by-64/65, or as oscillator buffer amplifier. The DIV1 pin controls this function. 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 50 load. 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 frequency 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.
( )(
)
CEFF =
1 1 1 2 C2 + C3 + C D1
+ C26
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 aircore micro springs yield low phase noise. Use a low tolerance inductor (L3) for predictable oscillation frequency. Resistors R6 and R7 can be chosen from 0 to 20 to 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
Power Management
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463 supports four different power-management features to conserve 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 0.5A, pull VCOON, DIV1, MOD, RXON, and TXON low.
MAX2420 MAX2421 MAX2422 MAX2460 MAX2463
LT
VCC
L4 100nH R7 C2
R5 1k 1/2 D1 R8 47k
L3
C26 C3 1/2 D1
VCO_CTRL C1 47pF
LT
R6
R4 1k D1 = ALPHA SMV1299-004
SEE FIGURE 1 FOR R6, R7, C2, C3, C26, AND L3 COMPONENT VALUES.
Figure 2. Oscillator Tank Schematic, Using the On-Chip VCO
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900MHz Image-Reject Transceivers MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
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 values 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 equivalent 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 chosen 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 50. 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.
VCC
Using an External Oscillator
CBLOCK 0.01F EXT LO
MAX2420 MAX2421 MAX2422 TANK MAX2460 MAX2463
50
VCC 50 EXTERNAL LO LEVEL IS 0dBm FROM A 50 SOURCE.
TANK
Figure 3. Using an External Local Oscillator
If an external 50 LO 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 50 source. For proper biasing of the oscillator input stage, the TANK and TANK pins must be pulled up to the VCC supply via 50 resistors. If the application requires overdriving the internal oscillator, 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
LT
TANK
L1
L3
R1
R2 Ci
L4 VTUNE C2 C1
VCC
LT TANK
L2
L5
R3
Figure 4. Series Coupled Resonant Tank for Wide Tuning Range and Low Phase Noise
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900MHz Image-Reject Transceivers
Functional Diagram
MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
LNAGAIN RXIN
90
0
RXOUT
CAP1 RXON TXON CAP2 BIAS
DIV1 MOD 0 90 /1/64/65 PREOUT PREGND TANK TANK VCOON 90 90
PHASE SHIFTER
MAX2420 MAX2421 MAX2422 MAX2460* MAX2463*
TXOUT *CRISS-CROSSED PHASE-SHIFTER CONNECTIONS
0
0 TXGAIN
TXIN
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13
900MHz Image-Reject Transceivers MAX2420/MAX2421/MAX2422/MAX2460/MAX2463
Package Information
SSOP.EPS
14
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