19-1448; Rev 4; 11/08
Low-Cost, Low-Voltage, PA Power Control
Amplifier for GSM Applications
MAX473
General Description
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 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.
♦ 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
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
♦ 1V to V
Current Sense Input Common-Mode
CC
Voltage Range
♦ No Phase-Reversal for Common-Mode Voltage
from 1V to V . The power control input and error
CC
from 0 to V
CC
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.
♦ External Current Sensing and Gain Setting
Resistors Maximize Flexibility
♦ Available in a Space-Saving 8-Pin µMAX
Ordering Information
Applications
GSM Cellular Phones
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 µMAX
MAX4473EUA
MAX4473ESA
Cordless Phones
8 SO
Precision Current Control
Pin Configuration appears at end of data sheet.
High-Frequency Servo Loops
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Typical Operating Circuit
V
CC
R
0.1μF
SENSE
RG1
RG2
A3
8
V
1
SR1
2
SR2
4
3
CC
PC
7
OUT
I
CCPA
A1
BUFFER
GC
IN
V-TO-I
CONVERTER
3R
R
ERROR
AMPLIFIER
V
CC
PA
Q1
A2
MAX4473
SHDN
GND
5
SR3
RFIN
V
· RG1
PC
6
I
=
CCPA
4 · RG3 · R
RG3
SENSE
________________________________________________________________ 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.