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19-0392; Rev 1; 5/96
UAL IT MAN TION K T VALUA A SHEE E T WS DA FOLLO
800MHz to 1000MHz Transmitter
_______________General Description
The MAX2402 transmitter integrates a double-balanced mixer, buffered local oscillator (LO) port, variable gain stage, and power amplifier into a single IC. It is intended for use in the 800MHz to 1000MHz band, and is compatible with both direct-sequence and frequencyhopping spread-spectrum designs in the 902MHz to 928MHz ISM band. In a typical application, a digital baseband signal is mixed with a local oscillator signal to yield a BPSKmodulated carrier at the antenna. Alternatively, the baseband input may be grounded and an FSKmodulated LO signal applied directly to the LO port. The LO port consists of a limiting amplifier that can accept a single-ended or differential signal with input power between -6dBm and +6dBm in the 800MHz to 1000MHz frequency range. The baseband modulation input is linear over a 2V range, and limits with larger signal levels within the supply range. The doublebalanced mixer has been optimized for high carrier rejection. The variable gain stage offers typically 40dB of adjustment range. The power amplifier provides more than 20dBm output power and has a bias adjustment, which allows adjustment of efficiency and harmonic distortion. A shutdown function reduces the current draw to less than 2A in less than 10s. The MAX2402 comes in a 20-pin SSOP package to minimize board area.
____________________________Features
o Low-Cost, Flexible Transmitter o More than 100mW of Output Power into 50 o Operates from 800MHz to 1000MHz o Single +5V Supply o 20-Pin SSOP Package o Uses Less than 2A in Power-Down o More than 35dB of Power Adjustment Range o LO Input Power Range from -6dBm to +6dBm o 2V Linear Range on Modulation Input
MAX2402
______________Ordering Information
PART MAX2402EAP* TEMP. RANGE -40C to +85C PIN-PACKAGE 20 SSOP
* An alternate marking, MAX2402CAP, has been identically tested.
________________________Applications
Direct-Sequence Spread-Spectrum Transmitter Frequency-Hopping Spread-Spectrum Transmitter FSK, GMSK, BPSK, and ASK Digital Transmitter AM and FM Analog Transmitter
__________________Pin Configuration
TOP VIEW
VGC MOD GND VCC
1 2 3 4 5 6 7 8 9
20 GND 19 VCC 18 GND 17 GND
________________Functional Diagram
VGC MODULATION BUFFER MOD MIXER VGC POWER AMPLIFIER OUT
GND LO+ LOGND
MAX2402
16 OUT 15 GND 14 OUT 13 GND 12 VCC 11 LGND
LO INPUT BUFFER LO+ LO-
SHDN MASTER BIAS SHDN BADJ
BADJ 10
SSOP
________________________________________________________________ Maxim Integrated Products
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For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
800MHz to 1000MHz Transmitter MAX2402
ABSOLUTE MAXIMUM RATINGS
VCC ........................................................................-0.3V to +6.5V Continuous Power Dissipation (TA = +70C) SSOP (derate 16.7mW/C above +70C) ......................1.33W Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +160C 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 = 4.75V to 5.5V, BADJ = open, SHDN = VCC - 0.5V, VGC = VCC, MOD = open, TA = -40C to +85C, unless otherwise noted.) PARAMETER Supply Current Shutdown Supply Current Supply Voltage Range VGC Input Bias Current MOD Bias Current SHDN Bias Current SHDN Low Threshold SHDN High Threshold SYMBOL ICC ICCPD VCC IVGC IMOD IPD VSHDN Low VSHDN High VCC - 0.5 VGC = VCC MOD = VCC MOD = 0V SHDN = VCC -320 10.5 0.5 SHDN = 0.5V 4.75 CONDITIONS Not transmitting MIN TYP 105 0.15 2 5.50 115 325 MAX UNITS mA A V A A A V V
AC ELECTRICAL CHARACTERISTICS
(MAX2402 evaluation kit, VCC = 5.0V, BADJ = 2V, SHDN = VCC, MOD = 0V, VGC = VCC, RLOAD = 35, fLO = 900MHz, LO power = -3dBm, TA = -40C to +85C, unless otherwise noted.) PARAMETER Supply Current Maximum Output Power Minimum Output Power Power Gain from LO LO Input Power Range LO Frequency Range MOD Usable Bandwidth VGC Control Range Carrier Suppression 2nd Harmonic Suppression 3rd Harmonic Suppression Output IP3 (BADJ = 1.0V) SYMBOL ICCAC PMAX PMIN PGAIN PLO fLO MODBW VGC CS HS2 HS3 IP3 For max power out (50 input term) (Note 2) (Note 2) (Note 2) (Note 2) MOD = 5Vp-p @ 100kHz (Note 1) (Note 1) fLO = 900MHz + 901MHz 1.0 30 22 25 28.4 -6 800 (Note 1) VGC = 0V (Note 1) CONDITIONS POUT = 20dBm (including current to load) MIN TYP 165 21 -19 24 6 1000 25 2.5 MAX UNITS mA dBm dBm dB dBm MHz MHz V dBC dBC dBC dBm
Note 1: See Typical Operating Characteristics graphs. Note 2: Guaranteed by design.
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800MHz to 1000MHz Transmitter
__________________________________________Typical Operating Characteristics
(MAX2402 evaluation kit, VCC = 5.0V, BADJ = 2V, SHDN = VCC, MOD = 0V, VGC = VCC, RLOAD = 35, fLO = 900MHz, LO power = -3dBm)
OUTPUT POWER vs. GAIN CONTROL VOLTAGE
MAX2402 TOC 1
MAX2402
OUTPUT POWER vs. FREQUENCY vs. TEMPERATURE
MAX2402 TOC 2
OUTPUT POWER vs. TEMPERATURE
MAX2402 TOC 3
25 20 OUTPUT POWER (dBm) 15 10 5 0 -5 -10 -15 -20 -25 1.0 1.5 VGC (V) 2.0
25 -40C +24C OUTPUT POWER (dBm) 23 +85C 21
22.0
OUTPUT POWER (dBm)
21.5
21.0
19
17
20.5 900MHz INPUT
15 2.5 800 820 840 860 880 900 920 940 960 980 FREQUENCY (MHz)
20.0 -50 -30 -10 10 30 50 70 90 TEMPERATURE (C)
OUTPUT POWER vs. BIAS CONTROL VOLTAGE vs. FREQUENCY
MAX2402 TOC 4
SUPPLY CURRENT vs. BIAS CONTROL VOLTAGE vs. FREQUENCY
240 SUPPLY CURRENT (mA) 800MHz 220 200 900MHz 180 160 140 120 100 990MHz
MAX2402 TOC 5
25 23 900MHz OUTPUT POWER (dBm) 21 19 17 15 13 11 9 7 0 1 2 3 990MHz
800MHz
260
4
5
0
1
2
3
4
5
BADJ VOLTAGE (V)
BADJ VOLTAGE (V)
AMPLITUDE OF 3rd & 5th HARMONICS OF MODULATED WAVEFORM
OUTPUT POWER BELOW FUNDAMENTAL (dBC) OUTPUT POWER (dBC) BELOW 900.1MHz (100kHz SINEWAVE MODULATION OF 900MHz LO) 42 TA = +85C 38 TA = +24C 34 900.5MHz 30 TA = -40C 26 TA = +85C 22 900.3MHz 18 TA = +24C
MAX2402 TOC 7
OUTPUT POWER LEVEL OF 2nd AND 3rd HARMONICS OF LO
(LO = 900MHz, -3dBm, MOD = 5V) 39 37 35 33 31 29 27 25 23 21 19 17 15 13 3rd HARMONIC T = -40C A TA = +24C
MAX2402 TOC 6
TA = +85C TA = +85C
TA = +24C TA = -40C 0.5 1.0 1.5 2.0 2.5
2nd HARMONIC
14 10
TA = -40C 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
3.0
3.5
4.0
MODULATION VOLTAGE, PEAK-TO-PEAK (V)
BADJ VOLTAGE (V)
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800MHz to 1000MHz Transmitter MAX2402
_____________________Pin Description
PIN 1 2 3, 5, 8, 13, 15, 17, 18, 20 4, 12, 19 6 7 9 NAME VGC MOD GND FUNCTION Variable Gain Control Input. Connect to VCC for maximum gain. Baseband Modulation Input to mixer Ground Supply Voltage, set between 4.75V and 5.5V Local-Oscillator Positive Input Local-Oscillator Negative Input Shutdown Control Input. Low level = off, high level = on. Bias Adjustment Control for power amplifier. Connect resistor from BADJ to V+ or GND (see Table 1). Connect 27nH inductor from LGND to GND to maximize output power. Power-Amplifier Output
MOD Input
The mixer's other port, the MOD input, remains linear over a 2V range from about 1.5V to 3.5V at the input. When driven with digital modulation (0V to 5V), this port will completely limit, resulting in a hard BPSKmodulated signal. Since this input is self biasing, carrier suppression can be improved by externally capacitively coupling the signal into the port (the MOD input resistance is approximately 10k). This would compensate for voltage offset or duty-cycle offset at this port, thus increasing carrier suppression. This MOD self bias is designed for very low on-chip offset, resulting in excellent carrier suppression. Since this port self biases when the signal is removed from MOD, the mixer will attenuate the output power by about 40dB, resulting in further attenuation past that attained from VGC control--a useful feature for ASK modulation.
VCC LO+ LOSHDN
VGC Stage
The mixer output drives the VGC stage. This stage attenuates through a multiplication technique that does not distort the signal with increased attenuation. VGC control is nonattenuating when connected to the V CC supply. VGC will attenuate for voltages from 2.5V to 1.0V. Most attenuation occurs between 1V and 2V. Maximum attenuation is achieved below 0.8V. Typical maximum attenuation is 40dB. At or beyond 40dB of attenuation, the signal may be slightly nonmonotonic. This means that there may be a slight upturn in the signal level at the low end of the VGC control range (typically about 1dB). Because of the stability implications, we suggest that the user not plan on attenuating past 35dB within a feedback loop.
10
BADJ
11 14, 16
LGND OUT
_______________Detailed Description
The MAX2402 transmitter is a versatile design that integrates several RF functions on a single IC. It has a wide variety of applications in portable and stationary wireless designs. Each of the functional blocks (shown in the Functional Diagram) is described in detail in the following sections.
Power Amplifier
The VGC stage passes the signal to the power amplifier. This class AB stage will produce at least 20dBm of output power for almost the complete transmit frequency range (with T A = +25C). See Typical Operating Characteristics.
LO Inputs
The LO inputs are internally capacitively coupled and self biasing. The LO port can be driven differentially or single ended. When terminated at the LO inputs with 50, the transmitter will provide full output power for LO inputs from -6dBm to +6dBm with single-ended drive, and -12dBm to +6dBm with differential drive. Input power beyond this range may saturate the LO input buffer, while input power below this range may result in less output power. The limiter is two cascaded differential stages, which also isolates the LO input from the mixer. This will help reduce any frequency-pulling effects in an external LO due to mixer loading. The limiter output drives one port of a double-balanced Gilbert mixer.
BADJ Input
The BADJ input adjusts the bias of the output stage. Increasing this voltage decreases bias current in the output devices, which increases efficiency, but also increases harmonic distortion (since the stage will be pushed further toward class B operation). Decreasing BADJ's voltage increases bias current in the output devices, resulting in higher output power and less harmonic distortion. Be sure to optimize BADJ for your application.
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_______________________________________________________________________________________
800MHz to 1000MHz Transmitter
BADJ can be left open or adjusted with a single pullup or pull-down resistor to VCC or GND, respectively. The value of this resistor determines the amount of adjustment applied. A single resistor results in no current flow at BADJ during power-down (whereas a resistor divider always has current flowing through the resistors). Table 1 shows the approximate bias adjust voltage at the pin for different resistor values. At lower LO frequencies, where the transmitter gain and output power is the highest, setting BADJ to a low voltage (maximum bias current) causes excessive current in the output and can cause unstable behavior in the IC. At lower LO frequencies (around 800MHz), more than 22dBm of power is easily obtained with BADJ set for 3V or more. If higher bias current and less distortion is desired in the 800MHz range, using a lower inductor value on LGND (pin 11) (see the Typical Application Circuit) might make the desired bias level stable. At higher frequencies (near 1000MHz), a lower bias level voltage results in more power (see the Output Power vs. Bias Control Voltage vs. Frequency graph in the Typical Operating Characteristics).
Power Amplifier Output
The power amplifier has an open-collector output that can drive into a load of 30 to 50; however, maximum power transfer is obtained at about 35. 27nH to ground is recommended on LGND (pin 11), as shown in the Typical Application Circuit. This inductor is used as a current source on the base of the output stage to pull stored charge out of the base.
MAX2402
SHDN Input
The SHDN input completely shuts down the current from the supply and all signal pins when switched below 0.5V. During normal operation, SHDN should remain above VCC - 0.5V. The shutdown control shuts down the total current to below 150nA (typ). Power-up occurs within 10s.
__________Applications Information
The MAX2402 transmitter operates within the 800MHz to 1000MHz frequency range. Figure 1 shows a typical application circuit. Additional applications information can be obtained from the MAX2402 evaluation kit manual.
Table 1. Bias-Adjust Voltage for Various Resistor Values
Resistor Value () 10k 20k 30k 40k 50k 100k 200k 300k 400k 500k 1M BADJ with Resistor Connected to GND (V)* 0.36 0.63 0.84 1.00 1.13 1.54 1.89 2.05 2.13 2.20 2.31 BADJ with Resistor Connected to VCC (V) 4.54 4.27 4.05 3.89
VARIABLE GAIN CONTROL MODULATION
1 VGC 2 3 MOD GND VCC GND GND
20 VCC 19 VCC GND GND 18 17 16 OUT 15 VCC 14 47nH 39pF 0.01F
VCC
39pF
4 5
MAX2402
50 6 VCO 7 50 8 SHUTDOWN CONTROL 9 10 BADJ 300k LGND GND SHDN GND VCC 13 12 11 39pF VCC LO+ LOGND OUT
3.75 3.34 3.00 2.85 2.75 2.68 2.57
27nH
* Typical variation of BADJ over temperature and process is less than 5%.
Figure 1. Typical Application Circuit
_______________________________________________________________________________________
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800MHz to 1000MHz Transmitter MAX2402
________________________________________________________Package Information
DIM INCHES MAX MIN 0.078 0.068 0.008 0.002 0.015 0.010 0.009 0.005 0.289 0.278 0.212 0.205 0.0256 BSC 0.311 0.301 0.037 0.022 8 0 MILLIMETERS MIN MAX 1.73 1.99 0.05 0.21 0.25 0.38 0.13 0.22 7.07 7.33 5.20 5.38 0.65 BSC 7.65 7.90 0.55 0.95 0 8
21-0003A
e
E
H
A A1 B C D E e H L
D A
0.127mm 0.004in.
B
A1
C
L
20-PIN SSOP SHRINK SMALL OUTLINE PACKAGE
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