19-1448; Rev 4; 11/08 Low-Cost, Low-Voltage, PA Power Control Amplifier for GSM Applications Features The MAX4473 PA power control IC is intended for closed-loop bias control of GSM power amplifiers. The device facilitates accurate control of the current delivered to the power amplifier (PA) through a control voltage. The error amplifier senses the voltage drop across an external current-sense resistor placed between the supply and the PA. The output of the error amplifier adjusts the PA gain until the current is proportional to the power control voltage applied to the MAX4473. This unique topology is useful in time-division-multipleaccess (TDMA) systems, such as GSM, where accurate transmit burst shaping and power control is required. User-selectable current sensing and gain setting resistors maximize flexibility. The MAX4473 operates from a single 2.7V to 6.5V supply and typically draws 1.2mA of supply current. The error amplifier has a common-mode range that extends from 1V to V CC . The power control input and error amplifier outputs swing rail-to-rail. A low-power shutdown mode reduces supply current to less than 1µA and activates an on-board active pull-down at the error amplifier output. Fast enable/disable times of 0.9µs reduce average power consumption without compromising dynamic performance. The MAX4473 is available in a space-saving 8-pin µMAX® package. ♦ Optimized for GSM Timing Requirements ♦ 2.7V to 6.5V Single-Supply Operation ♦ 1.2mA Supply Current ♦ ≤ 1µA Supply Current in Shutdown Mode ♦ Guaranteed 1.5µs Enable/Disable Times ♦ Active Output Pull-Down in Shutdown Mode ♦ Rail-to-Rail Error Amplifier Output ♦ Rail-to-Rail Power Control Input ♦ Output Drive Capability—500Ω and 300pF Loads ♦ 1V to VCC Current Sense Input Common-Mode Voltage Range ♦ No Phase-Reversal for Common-Mode Voltage from 0 to VCC ♦ External Current Sensing and Gain Setting Resistors Maximize Flexibility ♦ Available in a Space-Saving 8-Pin µMAX Ordering Information Applications PART GSM Cellular Phones Cordless Phones Precision Current Control High-Frequency Servo Loops TEMP RANGE PIN-PACKAGE MAX4473EUA -40°C to +85°C 8 µMAX MAX4473ESA -40°C to +85°C 8 SO Pin Configuration appears at end of data sheet. µMAX is a registered trademark of Maxim Integrated Products, Inc. Typical Operating Circuit VCC RSENSE 0.1μF RG1 8 VCC 4 PC RG2 1 SR1 2 SR2 A3 A1 BUFFER 3R V-TO-I CONVERTER R A2 OUT 7 ICCPA GC IN VCC ERROR AMPLIFIER PA Q1 MAX4473 3 SHDN GND 5 SR3 6 RG3 RFIN ICCPA = VPC · RG1 4 · RG3 · RSENSE ________________________________________________________________ Maxim Integrated Products 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. 1 MAX4473 General Description MAX4473 Low-Cost, Low-Voltage, PA Power Control Amplifier for GSM Applications ABSOLUTE MAXIMUM RATINGS VCC to GND..............................................................................7V SR1, SR2, SR3, PC, SHDN, OUT to GND ............................................-0.3V to (VCC + 0.3V) SR1 to SR3......................................................................0 to VCC OUT and SR3 Short-Circuit Duration to VCC or GND ........................................................Continuous Current into Any Pin..........................................................±50mA Continuous Power Dissipation (TA = +70°C) 8-Pin µMAX (derate 4.10mW/°C above +70°C) ............330mW 8-Pin SO (derate 5.88mW/°C above +70°C).................471mW Operating Temperature Range ...........................-40°C to +85°C Junction Temperature. .....................................................+150°C Storage Temperature Range. ............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C 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. ELECTRICAL CHARACTERISTICS (VCC = 2.7V to 6.5V, SHDN > 2.4V, MAX4473 test circuit, RG1 = RG2 = 1kΩ ±1%, RG3 = 2.5kΩ ±1%, RSENSE = 100Ω ±1%, RL = 10kΩ, CL = 300pF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 6.0V, VPC = 1.0V, TA = +25°C.) (Note 1) PARAMETER CONDITIONS MIN TYP MAX UNITS 6.5 V GENERAL Supply Voltage 2.7 Supply Current VPC = 0 1.2 2 mA Shutdown Supply Current SHDN < 0.4V, RL = 10Ω 0.03 1 µA SHDN Input High Voltage 2.4 V SHDN Input Low Voltage SHDN Input Current ERROR AMPLIFIER SR1, SR2 Input Offset Voltage SHDN = 0 to VCC ±0.5 ±2 1V < VSR1, VSR2 < VCC at +25°C ±0.5 ±1 1V < VSR1, VSR2 < VCC SR1, SR2 Input Common-Mode Voltage Range Inferred from CMRR test; VSR2 = GND (Note 2) SR1, SR2 Input Bias Current 1V < VSR1, VSR2 < VCC, VPC = GND, SR3 = unconnected SR1, SR2 Input Bias Offset Current SR1, SR2 Shutdown Leakage Current Power-Supply Rejection Ratio 10 µV/°C V ±0.04 ±1 µA 1V < VSR1, VSR2 < VCC, VPC = GND, SR3 = unconnected ±0.001 ±0.2 µA SHDN < 0.4V, VSR1 = VSR2 = VCC ±0.001 ±0.5 µA 1V < VSR1, VSR2 < VCC, VCC = 2.7V VPC = GND VCC = 6.5V 2.7V < VCC < 6.5V, VPC = GND RL = 10kΩ to VCC / 2 RL = 500Ω to VCC / 2 1 mV VCC Large-Signal Gain 2 V µA 1V < VSR1, VSR2 < VCC SR1, SR2 Input Offset Voltage Drift Common-Mode Rejection Ratio 0.4 ±0.5 65 85 75 95 80 90 VCC = 6.5V, 0.3V < VOUT < 6V 80 130 VCC = 2.7V, 0.3V < VOUT < 2.4V 80 125 VCC = 6.5V, 0.7V < VOUT < 5.5V 80 130 VCC = 2.7V, 0.7V < VOUT < 2.2V 80 120 _______________________________________________________________________________________ dB dB dB Low-Cost, Low-Voltage, PA Power Control Amplifier for GSM Applications (VCC = 2.7V to 6.5V, SHDN > 2.4V, MAX4473 test circuit, RG1 = RG2 = 1kΩ ±1%, RG3 = 2.5kΩ ±1%, RSENSE = 100Ω ±1%, RL = 10kΩ, CL = 300pF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 6.0V, VPC = 1.0V, TA = +25°C.) (Note 1) PARAMETER CONDITIONS RL = 10Ω to VCC / 2 MIN TYP MAX 0.15 VCC 0.15 0.5 VCC 0.5 UNITS V Output Voltage Swing RL = 500Ω to VCC / 2 Output Current Limit VOUT = VCC / 2 20 mA Gain-Bandwidth Product RL = 10Ω, CL = 300pF, fo = 10kHz 2 MHz Phase Margin RL = 10Ω, CL = 300pF 60 degrees Slew Rate Measured from 30% to 70% of VOUT, RL = 10Ω, CL = 300pF 1.8 V/µs Capacitive-Load Stability No sustained oscillations (Note 3) Enable/Disable Time From 50% of SHDN edge to VOUT = 1V, VPC = 2V 0 300 pF 0.9 1.5 µs ±0.04 ±1 µA GAIN CONTROL BUFFER AND V-TO-I CONVERTER PC Input Bias Current GND < VPC < VCC - 0.15V SR3 Output Current Limit VPC < 2.55V, SR1 = SR2 = VCC 0.750 4 VPC to VRG1 Ratio Measure voltage across RG1, 0.3V < VPC < 2.55V (Note 4) 0.095 0.1 PC Input Bandwidth Bandwidth from VPC to VRG1 2 mA 0.105 V/V MHz Note 1: Limits over temperature are guaranteed by design. Note 2: No output phase-reversal for input common-mode voltage range from GND to VCC. Common-mode range limited by voltage drop across Q1 and RG3. Note 3: Guaranteed by design. Note 4: Error dependent on tolerance of RG1, RG2, and RG3. Specified with 0.1% tolerance resistors. _______________________________________________________________________________________ 3 MAX4473 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (See Test Circuit, TA = +25°C, unless otherwise noted.) VRG1 / VPC RATIO vs. VPC RESPONSE SUPPLY CURRENT vs. SUPPLY VOLTAGE VCC = 6.0V 0.1075 0.1050 VRG1 / VPC (V/V) SUPPLY CURRENT (mA) TA = +25°C TA = +85°C 1.0 0.8 0.1025 0.1000 0.0975 0.0950 0.6 0.4 MAX4473 toc02 TA = -40°C 1.2 0.1100 MAX4473 toc01 1.4 SHDN = VCC PC = GND 0.0925 0.0900 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 0 1 2 3 SUPPLY VOLTAGE (V) 5 6 ENABLE/DISABLE TIME 40 PHASE 30 20 -90 ERROR AMPLIFIER 10 -108 0 SHDN 2V/div GND VCC = 6.5V VPC = 2V PHASE (degrees) 50 MAX4473 toc04 MAX4473 toc03 0 AVCL = 1000 -18 VCC = 6.5V VCM = VCC / 2 -36 VPC = 0 -54 GAIN -72 60 GAIN (dB) 4 VPC (V) ERROR-AMPLIFIER RESPONSE 70 -126 100kΩ -10 10kΩ -144 300pF 100Ω -20 -162 -30 10 100 1k 10k 100k 1M OUT 500mV/div GND -180 10M 500ns/div FREQUENCY (Hz) ERROR-AMPLIFIER OUTPUT LOW VOLTAGE vs. TEMPERATURE ERROR-AMPLIFIER OUTPUT HIGH VOLTAGE vs. TEMPERATURE VCC = 6.5V, RL = 500Ω to VCC / 2 0.25 0.40 MAX4473 toc06 0.45 MAX4473 toc05 0.30 VCC = 6.5V, RL = 500Ω to VCC / 2 0.35 0.15 VCC - VOH (V) 0.20 VOL (V) MAX4473 Low-Cost, Low-Voltage, PA Power Control Amplifier for GSM Applications VCC = 2.7V, RL = 500Ω to VCC / 2 0.10 0.05 0 -40 0.25 VCC = 2.7V, RL = 500Ω to VCC / 2 0.20 0.15 VCC = 2.7V, RL = 10kΩ to VCC / 2 VCC = 6.5V, RL = 10kΩ to VCC / 2 -15 10 35 TEMPERATURE (°C) 4 0.30 60 85 0.10 0.05 0 -40 VCC = 6.5V, RL = 10kΩ to VCC / 2 VCC = 2.7V, RL = 10kΩ to VCC / 2 -15 10 35 60 TEMPERATURE (°C) _______________________________________________________________________________________ 85 Low-Cost, Low-Voltage, PA Power Control Amplifier for GSM Applications PIN NAME FUNCTION 1 SR1 Inverting Input of Error Amplifier and Drain of V-to-I FET, Q1. Connect to supply side of current-sense resistor, RSENSE, through gain resistor RG1. 2 SR2 Noninverting Input of Error Amplifier. Connect to load side of current-sense resistor, RSENSE, through gain resistor RG2. Set RG2 equal to RG1. 3 SHDN Shutdown Input. Drive SHDN low to disable all amplifiers, pull OUT to GND, set the gate-to-source voltage of the V-to-I FET (Q1) to 0, and reduce supply current to less than 1µA. Drive high or connect to VCC for normal operation. 4 PC 5 GND Ground 6 SR3 Inverting Input to V-to-I Converter and Source of V-to-I FET, Q1. Connect to ground through gain resistor RG3. 7 OUT Output of Error Amplifier. Connect to gain control pin of power amplifier in bias control applications. 8 VCC +2.7V to +6.5V Voltage Supply Input. Bypass to ground with a 0.1µF capacitor. Power Control Input. Apply a voltage to PC to set a DC current through the sense resistor to control PA bias. Detailed Description The MAX4473 is a voltage-controlled, unidirectional, high-side current setting amplifier for applications where accurate control of PA supply current is desired. This device is intended for wireless TDMA based systems (GSM, DECT), where tight restrictions over the PA’s transmit burst and output power require closedloop control over the PA’s output power. When used with a PA, the MAX4473 functions as a voltage-controlled constant current source, accurately setting PA supply current by varying the gain of the PA. If you know the output power versus supply current profile for the PA, you can set the PA’s output power by controlling the amount of supply current delivered to the PA. The MAX4473 is composed of an input buffer (A1), a voltage-to-current converting amplifier (A2), and a railto-rail output error amplifier (A3) (see Typical Operating Circuit). External gain and sense resistors allow programmability for a wide range of applications. In the Typical Operating Circuit , PA supply current flows from the system supply, through the external current-sense resistor (RSENSE), to the PA. The rail-to-rail outputs of the error amplifier, A3, adjust the gain of the PA until the voltage drop across RSENSE equals the voltage drop across external gain resistor, RG1. The voltage drop across RG1 sets the voltage drop across RSENSE, with a larger voltage drop resulting in more current delivered to the PA. The voltage drop across RG1 is set by A1, A2, and the V-to-I FET, Q1. A voltage applied to the PC input of the input buffer is divided by four by a resistor-divider network. A2 forces its inverting input and the source of Q1 to VPC / 4, thus setting a voltage across RG3. The resulting current through RG3 sets the current through RG1. This unique architecture allows the supply current to be set independent of supply voltage. Set PA supply current according to the following equation: ICCPA = ( VPC · RG1 ) / ( 4 · RSENSE · RG3 ) Shutdown Mode When SHDN is a logic-level low (SHDN < 0.4V), amplifiers A1, A2, and A3 are off, Q1 is turned off, and the output of A3 is actively pulled to ground with an Nchannel FET. Supply current is reduced to less than 1µA in shutdown mode. Typical power-up time is 0.9µs and typical power-down time is 0.3µs, using the MAX4473 test circuit. _______________________________________________________________________________________ 5 MAX4473 Pin Description MAX4473 Low-Cost, Low-Voltage, PA Power Control Amplifier for GSM Applications Applications Information Gain Resistor Selection (RG1, RG2, RG3) For proper operation, do not make the value of external gain resistors RG1 and RG2 larger than twice the value of RG3. In most practical applications, choose RG1 smaller than RG3 to limit the voltage drop over RG1 and RSENSE. A large voltage drop over RSENSE substantially reduces the voltage applied to the PA, thus reducing PA output power. Set RG2 equal to RG1 to compensate for the input bias currents of A3. Recommended values for RG3 are between 1kΩ and 10kΩ. • Accuracy: A high RSENSE value allows lower currents to be measured more accurately because input offset voltages become less significant when the sense voltage is larger. For best performance, select RSENSE to provide approximately 100mV of sense voltage for the full-scale current in each application. • Efficiency and Power Dissipation: At high current levels, the I2R losses in RSENSE are significant. Take this into consideration when choosing the resistor value and its power dissipation (wattage) rating. Also, the sense resistor’s value may drift if it is allowed to heat up excessively. Sense Resistor Selection (RSENSE) Choose RSENSE based on the following criteria: • Voltage Loss: A high R SENSE value causes the power-source voltage to degrade through IR loss. For minimal voltage loss, use low RSENSE values. Pin Configuration _________________________Test Circuit TOP VIEW RSENSE VCC 100Ω 0.1% RG1 1kΩ 1% 0.1μF VCC PC SHDN GND SR1 RG2 1kΩ 1% SR2 MAX4473 2N3904 OUT RL 10kΩ SR3 RG3 2.5kΩ 1% CL 300pF SR1 1 8 VCC SR2 2 7 OUT 3 6 SR3 PC 4 5 GND MAX4473 SHDN RE 750Ω μMAX/SO Chip Information TRANSISTOR COUNT: 348 6 _______________________________________________________________________________________ Low-Cost, Low-Voltage, PA Power Control Amplifier for GSM Applications PACKAGE CODE DOCUMENT NO. 8 µMAX U8-1 21-0036 8 SO S8-2 21-0041 8LUMAXD.EPS PACKAGE TYPE α α _______________________________________________________________________________________ 7 MAX4473 Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Package Information (continued) For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. DIM A A1 B C e E H L N E H INCHES MILLIMETERS MAX MIN 0.069 0.053 0.010 0.004 0.014 0.019 0.007 0.010 0.050 BSC 0.150 0.157 0.228 0.244 0.016 0.050 MAX MIN 1.35 1.75 0.10 0.25 0.35 0.49 0.19 0.25 1.27 BSC 3.80 4.00 5.80 6.20 0.40 SOICN .EPS MAX4473 Low-Cost, Low-Voltage, PA Power Control Amplifier for GSM Applications 1.27 VARIATIONS: 1 INCHES TOP VIEW DIM D D D MIN 0.189 0.337 0.386 MAX 0.197 0.344 0.394 MILLIMETERS MIN 4.80 8.55 9.80 MAX 5.00 8.75 10.00 N MS012 8 AA 14 AB 16 AC D A B e C 0∞-8∞ A1 L FRONT VIEW SIDE VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, .150" SOIC APPROVAL DOCUMENT CONTROL NO. 21-0041 8 _______________________________________________________________________________________ REV. B 1 1 Low-Cost, Low-Voltage, PA Power Control Amplifier for GSM Applications REVISION NUMBER REVISION DATE 4 11/08 DESCRIPTION Removed QFN package PAGES CHANGED 1–9 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9 © 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc. MAX4473 Revision History