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PDF MAX4473EUA Data sheet ( Hoja de datos )
| Número de pieza | MAX4473EUA | |
| Descripción | Low-Cost / Low-Voltage / PA Power Control Amplifier for GSM Applications in 8-Pin MAX | |
| Fabricantes | Maxim Integrated | |
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19-1448; Rev 0; 3/99
Low-Cost, Low-Voltage, PA Power Control
Amplifier for GSM Applications in 8-Pin µMAX
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
extends from +1V to VCC. 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 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—500Ω and 300pF Loads
o +1V to VCC Current Sense Input Common-Mode
Voltage Range
o No Phase-Reversal for Common-Mode Voltage
from 0 to VCC
o External Current Sensing and Gain Setting
Resistors Maximize Flexibility
o 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
RG1
RSENSE
RG2
4 PC
A1
BUFFER
8
VCC
3R
3 SHDN
GND
5
R
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
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
1 page  
Low-Cost, Low-Voltage, PA Power Control
Amplifier for GSM Applications in 8-Pin µMAX
Sense Resistor Selection (RSENSE)
Choose RSENSE based on the following criteria:
• Voltage Loss: A high RSENSE value causes the
power-source voltage to degrade through IR loss.
For minimal voltage loss, use low RSENSE values.
• Accuracy: A high RSENSE value allows lower cur-
rents to be measured more accurately because input
offset voltages become less significant when the
sense voltage is larger. For best performance, select
RSENSE to provide approximately 100mV of sense
voltage for the full-scale current in each application.
• Efficiency and Power Dissipation: At high current
levels, the I2R losses in RSENSE are significant. Take
this into consideration when choosing the resistor
value and its power dissipation (wattage) rating.
Also, the sense resistor’s value may drift if it is
allowed to heat up excessively.
_________________________Test Circuit
VCC
0.1µF
RSENSE
RG1 100Ω
1k 0.1%
1%
RG2
1k
1%
VCC SR1
SR2
PC
SHDN
GND
MAX4473
SR3
RG3
2.5k
1%
OUT
RL
10k
CL
300pF
2N3904
RE
750Ω
TOP VIEW
Pin Configuration
SR1 1
SR2 2
SHDN 3
PC 4
MAX4473
8 VCC
7 OUT
6 SR3
5 GND
µMAX/SO
Chip Information
TRANSISTOR COUNT: 348
_______________________________________________________________________________________ 5
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