Datasheet MAX4473 Datasheet (MAXIM)

Page 1

General Description

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

. 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.

Applications

GSM Cellular Phones

Cordless Phones

Precision Current Control

High-Frequency Servo Loops

Features

♦ 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 V

Current Sense Input Common-Mode

Voltage Range

♦ No Phase-Reversal for Common-Mode Voltage

from 0 to V

♦ External Current Sensing and Gain Setting

Resistors Maximize Flexibility

♦ Available in a Space-Saving 8-Pin µMAX

MAX4473

Low-Cost, Low-Voltage, PA Power Control

Amplifier for GSM Applications

________________________________________________________________

Maxim Integrated Products

Typical Operating Circuit

19-1448; Rev 4; 11/08

Pin Configuration appears at end of data sheet.

Ordering Information

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.

µMAX is a registered trademark of Maxim Integrated Products, Inc.

0.1μF RG1 RG2

SENSE

PART TEMP RANGE PIN-PACKAGE

MAX4473EUA -40°C to +85°C 8 µMAX

MAX4473ESA -40°C to +85°C 8 SO

8 V

BUFFER

SHDN

GND

V-TO-I

CONVERTER

SR1 SR2

SR3

RG3

ERROR

AMPLIFIER

MAX4473

OUT



GC IN

RFIN

CCPA

· RG1

CCPA

4 · RG3 · R

SENSE

Page 2

MAX4473

Low-Cost, Low-Voltage, PA Power Control Amplifier for GSM Applications

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= 2.7V to 6.5V, SHDN > 2.4V, MAX4473 test circuit, RG1 = RG2 = 1kΩ ±1%, RG3 = 2.5kΩ ±1%, R

SENSE

= 100Ω ±1%,

= 10kΩ, CL= 300pF, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= 6.0V, VPC= 1.0V, TA= +25°C.) (Note 1)

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.

VCCto GND..............................................................................7V

SR1, SR2, SR3, PC, SHDN,

OUT to GND ............................................-0.3V to (V

+ 0.3V)

SR1 to SR3......................................................................0 to V

OUT and SR3 Short-Circuit Duration

to V

or GND ........................................................Continuous

Current into Any Pin..........................................................±50mA

Continuous Power Dissipation (T

= +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

PARAMETER CONDITIONS MIN TYP MAX UNITS

GENERAL

Supply Voltage 2.7 6.5 V

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 0.4 V SHDN Input Current SHDN = 0 to V

ERROR AMPLIFIER

SR1, SR2 Input Offset Voltage

SR1, SR2 Input Offset Voltage Drift

SR1, SR2 Input Common-Mode Voltage Range

1V < V

Inferred from CMRR test; V

SR1, SR2 Input Bias Current 1V < V

SR1, SR2 Input Bias Offset Current

SR1, SR2 Shutdown Leakage Current

Common-Mode Rejection Ratio

1V < V

SHDN < 0.4V, V

1V < V V

SR1

= GND

, V

< V

SR2

, V

< VCC at +25°C ±0.5 ±1

SR2

, V

< V

SR2

= GND (Note 2) 1 V

SR2

, V

< VCC, VPC = GND, SR3 = unconnected ±0.04 ±1 µA

SR2

, V

< VCC, VPC = GND, SR3 = unconnected ±0.001 ±0.2 µA

SR2

= V

SR2

VCC = 2.7V 65 85

= 6.5V 75 95

, V

SR2

SR1

< VCC,

±0.5 ±2

±0.001 ±0.5 µA

Power-Supply Rejection Ratio 2.7V < VCC < 6.5V, VPC = GND 80 90 dB

Large-Signal Gain

RL = 10kΩ to VCC / 2

= 500Ω to VCC / 2

VCC = 6.5V, 0.3V < V

= 2.7V , 0.3V < V

C C

= 6.5V , 0.7V < V

C C

= 2.7V , 0.7V < V

C C

< 6V 80 130

OUT

< 2.4V 80 125

OU T

< 5.5V 80 130

OU T

< 2.2V 80 120

OU T

±0.5 µA

µV/°C

Page 3

MAX4473

Low-Cost, Low-Voltage, PA Power Control

Amplifier for GSM Applications

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= 2.7V to 6.5V, SHDN > 2.4V, MAX4473 test circuit, RG1 = RG2 = 1kΩ ±1%, RG3 = 2.5kΩ ±1%, R

SENSE

= 100Ω ±1%,

= 10kΩ, CL= 300pF, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= 6.0V, VPC= 1.0V, TA= +25°C.) (Note 1)

Note 1: Limits over temperature are guaranteed by design. Note 2: No output phase-reversal for input common-mode voltage range from GND to V

. 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.

Output Voltage Swing

Output Current Limit V

Gain-Bandwidth Product RL = 10Ω, CL = 300pF, fo = 10kHz 2 MHz

Phase Margin RL = 10Ω, CL = 300pF 60 degrees

Slew Rate

Capacitive-Load Stability No sustained oscillations (Note 3) 0 300 pF Enable/Disable Time From 50% of SHDN edge to V

GAIN CONTROL BUFFER AND V-TO-I CONVERTER

PC Input Bias Current GND < VPC < VCC - 0.15V ±0.04 ±1 µA

SR3 Output Current Limit VPC < 2.55V, SR1 = SR2 = V

VPC to VRG1 Ratio

PC Input Bandwidth Bandwidth from VPC to V

PARAMETER CONDITIONS MIN TYP MAX UNITS

RL = 10Ω to VCC / 2 0.15

= 500Ω to VCC / 2 0.5

= VCC / 2 20 mA

OUT

Measured from 30% to 70% of V

= 10Ω, CL = 300pF

Measure voltage across RG1,

0.3V < V

< 2.55V (Note 4)

RG1

OUT

= 1V, VPC = 2V 0.9 1.5 µs

OUT

1.8 V/µs

0.750 4 mA

0.095 0.1 0.105 V/V

2 MHz

0.15

0.5

Page 4

MAX4473

Low-Cost, Low-Voltage, PA Power Control Amplifier for GSM Applications

4 _______________________________________________________________________________________

Typical Operating Characteristics

(See

Test Circuit

, TA= +25°C, unless otherwise noted.)

0.4

0.6

1.0

0.8

1.2

1.4

2.5 3.5 4.03.0 4.5 5.0 5.5 6.0 6.5

SUPPLY CURRENT vs. SUPPLY VOLTAGE

MAX4473 toc01

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

TA = -40°C

TA = +25°C

TA = +85°C

SHDN = V

PC = GND

0.0900

0.0925

0.0950

0.0975

0.1000

0.1025

0.1050

0.1075

0.1100

021 3456

RG1

/ VPC RATIO vs. VPC RESPONSE

MAX4473 toc02

VPC (V)

RG1

/ V

(V/V)

VCC = 6.0V

70 0

-30 10 100 1k 10k 100k 1M

10M

ERROR-AMPLIFIER RESPONSE

-10

-20

MAX4473 toc03

FREQUENCY (Hz)

GAIN (dB)

PHASE (degrees)

-180

-144

-126

-162

-108

-90

-72

-54

-36

-18

PHASE

GAIN

VCL

= 1000

= 6.5V

= V

/ 2

= 0

100kΩ

ERROR AMPLIFIER

100Ω

10kΩ

300pF

OUT

500mV/div

SHDN

2V/div

ENABLE/DISABLE TIME

MAX4473 toc04

500ns/div

VCC = 6.5V V

= 2V

GND

0.10

0.05

0.20

0.15

0.25

0.30

-40 10-15 35 60 85

ERROR-AMPLIFIER

OUTPUT LOW VOLTAGE vs. TEMPERATURE

MAX4473 toc05

TEMPERATURE (°C)

(V)

VCC = 6.5V, RL = 10kΩ to V

/ 2

VCC = 2.7V, RL = 10kΩ to V

/ 2

VCC = 6.5V, RL = 500Ω to V

/ 2

VCC = 2.7V, RL = 500Ω to V

/ 2

0.15

0.10

0.05

0.25

0.20

0.35

0.30

0.40

0.45

-40 10-15 35 60 85

ERROR-AMPLIFIER

OUTPUT HIGH VOLTAGE vs. TEMPERATURE

MAX4473 toc06

TEMPERATURE (°C)

(V)

VCC = 2.7V, RL = 10kΩ to V

/ 2

VCC = 6.5V, RL = 500Ω to V

/ 2

VCC = 6.5V, RL = 10kΩ to V

/ 2

VCC = 2.7V, RL = 500Ω to V

/ 2

Page 5

MAX4473

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 pro-

grammability 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 (R

SENSE

), to the PA. The rail-to-rail

outputs of the error amplifier, A3, adjust the gain of the

PA until the voltage drop across R

SENSE

equals the voltage drop across external gain resistor, RG1. The voltage drop across RG1 sets the voltage drop across R

SENSE

, 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:

CCPA

= ( VPC· RG1 ) / ( 4 · R

SENSE

· 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.

Pin Description

Low-Cost, Low-Voltage, PA Power Control

Amplifier for GSM Applications

_______________________________________________________________________________________ 5

PIN NAME FUNCTION

1 SR1

2 SR2

3 SHDN

4PC

5 GND Ground

6 SR3

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.

Inverting Input of Error Amplifier and Drain of V-to-I FET, Q1. Connect to supply side of current-sense resistor, R

Noninverting Input of Error Amplifier. Connect to load side of current-sense resistor, R gain resistor RG2. Set RG2 equal to RG1.

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 V

for normal operation.

Power Control Input. Apply a voltage to PC to set a DC current through the sense resistor to control PA bias.

Inverting Input to V-to-I Converter and Source of V-to-I FET, Q1. Connect to ground through gain resistor RG3.

, through gain resistor RG1.

SENSE

, through

SENSE

Page 6

MAX4473

Low-Cost, Low-Voltage, PA Power Control Amplifier for GSM Applications

6 _______________________________________________________________________________________

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 R

SENSE

. A large voltage drop over R

SENSE

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.

Sense Resistor Selection (R

SENSE

)

Choose R

SENSE

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 R

SENSE

values.

• Accuracy: A high R

SENSE

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 R

SENSE

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 R

SENSE

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.

_________________________Test Circuit

Pin Configuration

Chip Information

TRANSISTOR COUNT: 348

SR1

MAX4473

SR3

RG3

2.5kΩ 1%

SENSE

100Ω

0.1%

SR2

OUT

RG2 1kΩ 1%

10kΩ

300pF

750Ω

0.1μF

SHDN

GND

RG1 1kΩ 1%

2N3904

TOP VIEW

SR1

SHDN

MAX4473

μMAX/SO

87V

OUTSR2

SR3

GNDPC

Page 7

MAX4473

Low-Cost, Low-Voltage, PA Power Control

Amplifier for GSM Applications

_______________________________________________________________________________________ 7

Package Information

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

Low-Cost, Low-Voltage, PA Power Control

Amplifier for GSM Applications

MAX4473

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.

8 µMAX U8-1

21-0036

8 SO S8-2

21-0041

8LUMAXD.EPS

Page 8

MAX4473

Low-Cost, Low-Voltage, PA Power Control Amplifier for GSM Applications

8 _______________________________________________________________________________________

Package Information (continued)

For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.

TOP VIEW

FRONT VIEW

INCHES

DIM

MIN

0.053A

0.004

0.014

0.007

C e 0.050 BSC 1.27 BSC

0.150

E H 0.2440.228 5.80 6.20

0.016L

VARIATIONS:

INCHES

MINDIM

0.189 0.197 AA5.004.80 8

0.337 0.344 AB8.758.55 14

0∞-8∞

MAX

0.069

0.010

0.019

0.010

0.157

0.050

MAX

0.3940.386D

MILLIMETERS

MAX

MIN

1.35

1.75

0.10

0.25

0.35

0.49

0.19

0.25

3.80 4.00

0.40 1.27

MILLIMETERS

MAX

MIN

9.80 10.00

N MS012

SOICN .EPS

SIDE VIEW

PROPRIETARY INFORMATION

TITLE:

PACKAGE OUTLINE, .150" SOIC

REV.DOCUMENT CONTROL NO.APPROVAL

21-0041

Page 9

Low-Cost, Low-Voltage, PA Power Control

Amplifier for GSM Applications

MAX4473

Revision History

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 _____________________

REVISION

NUMBER

4 11/08 Removed QFN package 1–9

REVISION

DATE

DESCRIPTION

PAGES

CHANGED