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 V
CC
. 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.
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
Ordering Information
PART
MAX4473EUA
MAX4473ESA
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 µMAX
8 SO
Applications
GSM Cellular Phones
Cordless Phones
Precision Current Control
High-Frequency Servo Loops
µMAX is a registered trademark of Maxim Integrated Products, Inc.
V
CC
0.1μF
RG1
8
V
CC
A1
BUFFER
3R
V-TO-I
CONVERTER
A2
Q1
1
SR1
2
SR2
A3
R
SENSE
RG2
Pin Configuration appears at end of data sheet.
Typical Operating Circuit
4 PC
OUT
7
GC
IN V
CC
PA
I
CCPA
ERROR
AMPLIFIER
R
3 SHDN
GND
5
MAX4473
SR3
6
RG3
RFIN
I
CCPA
=
V
PC
·
RG1
4
·
RG3
·
R
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.
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