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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) via 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-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

supply and typically draws 1.2mA of supply current.

The error amplifier has a common-mode range that

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 com-

promising 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

o Optimized for GSM Timing Requirements

o +2.7V to +6.5V Single-Supply Operation

o 1.2mA Supply Current

o

≤1µA Supply Current in Shutdown Mode

o Guaranteed 1.5µs Enable/Disable Times

o Active Output Pull-Down in Shutdown Mode

o Rail-to-Rail Error Amplifier Output

o Rail-to-Rail Power Control Input

o Output Drive Capability—500

Ω and 300pF Loads

Voltage Range

o No Phase-Reversal for Common-Mode Voltage

o External Current Sensing and Gain Setting

Resistors Maximize Flexibility

o Available in a Space-Saving 8-pin µMAX

Low-Cost, Low-Voltage, PA Power Control

Amplifier for GSM Applications in 8-Pin µMAX

________________________________________________________________

Maxim Integrated Products

1

GND

PC

0.1

µF

8

7

R

3R

A3

PA

GC

IN

RFIN

4

3 SHDN

BUFFER

5

6

A2

Q1

A1

12

SR1

SR2

SR3

RG3

OUT

V-TO-I

CONVERTER

ERROR

AMPLIFIER

RG1

RG2

MAX4473

Typical Operating Circuit

19-1448; Rev 0; 3/99

PART

MAX4473EUA

MAX4473ESA

-40°C to +85°C

-40°C to +85°C

TEMP. RANGE

PIN-PACKAGE

8 µMAX

8 SO

Pin Configuration appears at end of data sheet.

Ordering Information

Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.