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MAX4473

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

Maxim Integrated 

19-1448; Rev 4; 11/08

Low-Cost, Low-Voltage, PA Power Control

Amplifier for GSM Applications

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 deliv-

ered to the power amplifier (PA) through a control volt-

age. 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-multiple-

access (TDMA) systems, such as GSM, where accurate

transmit burst shaping and power control is required.

User-selectable current sensing and gain setting resis-

tors maximize flexibility.

The MAX4473 operates from a single 2.7V to 6.5V sup-

ply and typically draws 1.2mA of supply current. The

error amplifier has a common-mode range that extends

from 1V to VCC. The power control input and error

amplifier outputs swing rail-to-rail. A low-power shut-

down 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 compro-

mising dynamic performance. The MAX4473 is avail-

able in a space-saving 8-pin µMAX® package.

Applications

GSM Cellular Phones

Cordless Phones

Precision Current Control

High-Frequency Servo Loops

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

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 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

PART

MAX4473EUA

MAX4473ESA

TEMP RANGE

-40°C to +85°C

-40°C to +85°C

PIN-PACKAGE

8 µMAX

8 SO

Pin Configuration appears at end of data sheet.

Typical Operating Circuit

VCC

0.1μF

RSENSE

RG1

RG2

4 PC

8

VCC

A1

BUFFER

3R

R

3 SHDN

GND

5

12

SR1 SR2

V-TO-I

CONVERTER

A2

Q1

SR3

6

RG3

OUT 7

A3

ERROR

AMPLIFIER

GC

IN VCC

PA

MAX4473

RFIN

ICCPA

ICCPA

=

4

·

VPC ·

RG3 ·

RG1

RSENSE

________________________________________________________________ Maxim Integrated Products 1

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.

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