MAXIM MAX4473 Technical data

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

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.

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

CC

Current Sense Input Common-Mode

Voltage Range

♦ No Phase-Reversal for Common-Mode Voltage

from 0 to V

CC

♦ 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

1

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.

V

CC

0.1μF
RG1 RG2

R

SENSE

PART TEMP RANGE PIN-PACKAGE

MAX4473EUA -40°C to +85°C 8 µMAX

MAX4473ESA -40°C to +85°C 8 SO

8
V

4

PC

A1

BUFFER

3

SHDN

GND

5

CC

3R

R

V-TO-I

CONVERTER

A2

12

SR1 SR2

Q1

SR3

6

RG3

A3

ERROR

AMPLIFIER

MAX4473

OUT



7

GC
IN

RFIN

I

CCPA

V

CC

PA

V

· RG1

CCPA

=

4 · RG3 · R

PC

SENSE

I

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%,

R

L

= 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

CC

+ 0.3V)

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

CC

OUT and SR3 Short-Circuit Duration

to V

CC

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

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

Continuous Power Dissipation (T

A

= +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

CC

ERROR AMPLIFIER

SR1, SR2 Input Offset Voltage

SR1, SR2 Input Offset Voltage
Drift

SR1, SR2 Input Common-Mode
Voltage Range

1V < V

1V < V

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

PC

SR1

SR1

SR1

SR1

SR1

SR1

= GND

, V

< V

SR2

CC

, V

< VCC at +25°C ±0.5 ±1

SR2

, V

< V

SR2

CC

= 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

= V

SR2

CC

VCC = 2.7V 65 85

V

= 6.5V 75 95

CC

, V

SR2

SR1

< VCC,

±0.5 ±2

10

±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

R

= 500Ω to VCC / 2

L

VCC = 6.5V, 0.3V < V

= 2.7V , 0.3V < V

V

C C

V

= 6.5V , 0.7V < V

C C

= 2.7V , 0.7V < V

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

CC

mV

µV/°C

V

dB

dB

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%,

R

L

= 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

CC

. 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

R

L

= VCC / 2 20 mA

OUT

Measured from 30% to 70% of V

= 10Ω, CL = 300pF

R

L

Measure voltage across RG1,

0.3V < V

< 2.55V (Note 4)

PC

RG1

,

OUT

= 1V, VPC = 2V 0.9 1.5 µs

OUT

CC

1.8 V/µs

0.750 4 mA

0.095 0.1 0.105 V/V

2 MHz

V

V

-

CC

0.15

-

CC

0.5

V