MAXIM MAX4473EGA

19-1448; Rev 1; 1/02
Low-Cost, Low-Voltage, PA Power Control
Amplifier for GSM Applications in 8-Pin QFN
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 QFN
Ordering Information
PART
Applications
GSM Cellular Phones
Cordless Phones
Precision Current Control
High-Frequency Servo Loops
TEMP RANGE
PIN-PACKAGE
MAX4473EUA
-40°C to +85°C
8 µMAX
MAX4473EGA
-40°C to +85°C
8 QFN
MAX4473ESA
-40°C to +85°C
8 SO
Pin Configuration appears at end of data sheet.
Typical Operating Circuit
VCC
RSENSE
0.1µF
RG1
8
VCC
4 PC
RG2
1
SR1
2
SR2
A3
A1
BUFFER
3R
V-TO-I
CONVERTER
R
A2
OUT
7
ICCPA
GC
IN VCC
ERROR
AMPLIFIER
PA
Q1
MAX4473
3 SHDN
GND
5
SR3
6
RG3
RFIN
ICCPA =
VPC · RG1
4 · RG3 · RSENSE
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
________________________________________________________________ Maxim Integrated Products
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.
1
MAX4473
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 delivered to the power amplifier (PA) through 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-multipleaccess (TDMA) systems, such as GSM, where accurate
transmit burst shaping and power control is required.
User-selectable current sensing and gain setting resistors 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 V CC . 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 compromising dynamic performance. The MAX4473 is available in a space-saving 8-pin QFN package.
MAX4473
Low-Cost, Low-Voltage, PA Power Control
Amplifier for GSM Applications in 8-Pin QFN
ABSOLUTE MAXIMUM RATINGS
VCC to GND..............................................................................7V
SR1, SR2, SR3, PC, SHDN,
OUT to GND ............................................-0.3V to (VCC + 0.3V)
SR1 to SR3......................................................................0 to VCC
OUT and SR3 Short-Circuit Duration
to VCC or GND ........................................................Continuous
Current into Any Pin..........................................................±50mA
Continuous Power Dissipation (TA = +70°C)
8-Pin µMAX (derate 4.10mW/°C above +70°C) ............330mW
8-Pin QFN (derate 24.4mW/°C above +70°C) ............1951mW
8-Pin SO (derate 5.88mW/°C above +70°C).................471mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature. .....................................................+150°C
Storage Temperature Range. ............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = 2.7V to 6.5V, SHDN > 2.4V, MAX4473 test circuit, RG1 = RG2 = 1kΩ ±1%, RG3 = 2.5kΩ ±1%, RSENSE = 100Ω ±1%,
RL = 10kΩ, CL = 300pF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 6.0V, VPC = 1.0V, TA = +25°C.)
(Note 1)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
GENERAL
Supply Voltage
2.7
Supply Current
VPC = 0
Shutdown Supply Current
SHDN < 0.4V, RL = 10kΩ
SHDN Input High Voltage
6.5
V
1.2
2
mA
0.03
1
µA
2.4
V
SHDN Input Low Voltage
SHDN Input Current
SHDN = 0 to VCC
0.4
V
±0.5
µA
ERROR AMPLIFIER
SR1, SR2 Input Offset Voltage
1V < VSR1, VSR2 < VCC
±0.5
SR1, SR2 Input Offset Voltage Drift
1V < VSR1, VSR2 < VCC
10
SR1, SR2 Input Common-Mode
Voltage Range
Inferred from CMRR test; VPC = GND (Note 2)
SR1, SR2 Input Bias Current
1V < VSR1, VSR2 < VCC, VPC = GND,
SR3 = unconnected
SR1, SR2 Input Bias Offset Current
mV
µV/°C
VCC
V
±0.04
±1
µA
1V < VSR1, VSR2 < VCC, VPC = GND,
SR3 = unconnected
±0.001
±0.2
µA
SR1, SR2 Shutdown Leakage Current
SHDN < 0.4V, VSR1 = VSR2 = VCC
±0.001
±0.5
µA
Common-Mode Rejection Ratio
1V < VSR1, VSR2 < VCC,
VPC = GND
1
Output Current Limit
VCC = 2.7V
VCC = 6.5V
2.7V < VCC < 6.5V, VPC = GND
VCC = 6.5V, 0.3V < VOUT < 6V
RL = 10kΩ
to VCC / 2
VCC = 2.7V, 0.3V < VOUT < 2.4V
VCC = 6.5V, 0.7V < VOUT < 5.5V
RL = 500Ω
to VCC / 2
VCC = 2.7V, 0.7V < VOUT < 2.2V
RL = 10kΩ to VCC / 2
RL = 500Ω to VCC / 2
VOUT = VCC / 2
20
mA
Gain-Bandwidth Product
RL = 10kΩ, CL = 300pF, fo = 10kHz
2
MHz
Phase Margin
RL = 10kΩ, CL = 300pF
60
degrees
Slew Rate
Measured from 30% to 70% of VOUT, RL = 10kΩ,
CL = 300pF
1.8
V/µs
Power-Supply Rejection Ratio
Large-Signal Gain
Output Voltage Swing
2
±2
65
75
80
80
80
80
80
0.15
0.5
85
95
90
130
125
130
120
dB
dB
dB
VCC - 0.15
VCC - 0.5
_______________________________________________________________________________________
V
Low-Cost, Low-Voltage, PA Power Control
Amplifier for GSM Applications in 8-Pin QFN
(VCC = 2.7V to 6.5V, SHDN > 2.4V, MAX4473 test circuit, RG1 = RG2 = 1kΩ ±1%, RG3 = 2.5kΩ ±1%, RSENSE = 100Ω ±1%,
RL = 10kΩ, CL = 300pF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = 6.0V, VPC = 1.0V, TA = +25°C.)
(Note 1)
PARAMETER
CONDITIONS
MIN
Capacitive-Load Stability
No sustained oscillations (Note 3)
Enable/Disable Time
From 50% of SHDN edge to VOUT = 1V, VPC = 2V
TYP
MAX
UNITS
300
pF
0.9
1.5
µs
±0.04
±1
0
GAIN CONTROL BUFFER AND V-TO-I CONVERTER
PC Input Bias Current
GND < VPC < VCC - 0.15V
SR3 Output Current Limit
VPC = 2.55V, SR1 = SR2 = VCC
0.750
4
VPC to VRG1 Ratio
Measure voltage across RG1, 0.3V < VPC < 2.55V (Note 4)
0.095
0.1
PC Input Bandwidth
Bandwidth from VPC to VRG1
µA
mA
0.105
2
V/V
MHz
Note 1: Limits over temperature are guaranteed by design.
Note 2: No output phase-reversal for input common-mode voltage range from GND to VCC. Common-mode range limited by voltage
drop across Q1 and RG3.
Note 3: Guaranteed by design.
Note 4: Error dependent on tolerance of RG1, RG2, and RG3. Specified with 0.1% tolerance resistors.
Typical Operating Characteristics
(See Test Circuit, TA = +25°C, unless otherwise noted.)
VRG1 / VPC RATIO vs. VPC RESPONSE
TA = +25°C
50
40
0.1025
GAIN (dB)
VRG1 / VPC (V/V)
0.8
0
AVCL = 1000
-18
VCC = 6.5V
VCM = VCC / 2
-36
VPC = 0
-54
GAIN
-72
60
0.1050
TA = +85°C
1.0
0.1075
0.1000
0.0975
PHASE
30
-90
20
ERROR
AMPLIFIER
10
-108
0
0.0950
0.0925
3.5
4.0
4.5
5.0
5.5
6.0
0
6.5
1
2
3
4
5
10
6
-162
100
1k
10k
100k
1M
-180
10M
SUPPLY VOLTAGE (V)
VPC (V)
FREQUENCY (Hz)
ENABLE/DISABLE TIME
ERROR-AMPLIFIER
OUTPUT LOW VOLTAGE vs. TEMPERATURE
ERROR-AMPLIFIER
OUTPUT HIGH VOLTAGE vs. TEMPERATURE
0.30
SHDN
2V/div
0.45
MAX4473 toc05
3.0
-144
300pF
-30
0.0900
2.5
10kΩ
100Ω
-20
VCC = 6.5V, RL = 500Ω to VCC / 2
0.25
0.40
VOL (V)
0.20
0.15
VCC = 2.7V, RL = 500Ω to VCC / 2
GND
500ns/div
0.05
0
-40
0.30
0.25
VCC = 2.7V, RL = 500Ω to VCC / 2
0.20
0.15
0.10
OUT
500mV/div
VCC = 6.5V, RL = 500Ω to VCC / 2
0.35
GND
VCC = 6.5V
VPC = 2V
VCC - VOH (V)
0.4
SHDN = VCC
PC = GND
-126
100kΩ
-10
MAX4473 toc06
0.6
MAX4473 toc04
SUPPLY CURRENT (mA)
1.2
VCC = 6.0V
MAX4473 toc03
70
MAX4473 toc02
MAX4473 toc01
TA = -40°C
ERROR-AMPLIFIER RESPONSE
0.1100
PHASE (degrees)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
1.4
VCC = 2.7V, RL = 10kΩ to VCC / 2
VCC = 6.5V, RL = 10kΩ to VCC / 2
-15
10
35
TEMPERATURE (°C)
60
85
0.10
0.05
0
-40
VCC = 6.5V, RL = 10kΩ to VCC / 2
VCC = 2.7V, RL = 10kΩ to VCC / 2
-15
10
35
60
85
TEMPERATURE (°C)
_______________________________________________________________________________________
3
MAX4473
ELECTRICAL CHARACTERISTICS (continued)
Low-Cost, Low-Voltage, PA Power Control
Amplifier for GSM Applications in 8-Pin QFN
MAX4473
Pin Description
PIN
NAME
FUNCTION
1
SR1
Inverting Input of Error Amplifier and Drain of V-to-I FET, Q1. Connect to supply side of current-sense resistor, RSENSE, through gain resistor RG1.
2
SR2
Noninverting Input of Error Amplifier. Connect to load side of current-sense resistor, RSENSE, through gain
resistor RG2. Set RG2 equal to RG1.
3
SHDN
Shutdown Input. Drive SHDN low to disable all amplifiers, pull OUT to GND, set the gate-to-source voltage
of the V-to-I FET (Q1) to 0, and reduce supply current to less than 1µA. Drive high or connect to VCC for normal operation.
4
PC
Power Control Input. Apply a voltage to PC to set a DC current through the sense resistor to control PA bias.
5
GND
Ground
6
SR3
Inverting Input of V-to-I Converter and Source of V-to-I FET, Q1. Connect to ground through gain resistor
RG3.
7
OUT
Output of Error Amplifier. Connect to gain control pin of power amplifier in bias control applications.
8
VCC
+2.7V to +6.5V Voltage Supply Input. Bypass to ground with a 0.1µF capacitor.
Detailed Description
The MAX4473 is a voltage-controlled, unidirectional,
high-side current setting amplifier for applications
where accurate control of PA supply current is desired.
This device is intended for wireless TDMA based systems (GSM, DECT), where tight restrictions over the
PA’s transmit burst and output power require closedloop control over the PA’s output power. When used
with a PA, the MAX4473 functions as a voltage-controlled constant current source, accurately setting PA
supply current by varying the gain of the PA. If you
know the output power versus supply current profile for
the PA, you can set the PA’s output power by controlling the amount of supply current delivered to the PA.
The MAX4473 is composed of an input buffer (A1), a
voltage-to-current converting amplifier (A2), and a railto-rail output error amplifier (A3) (see Typical Operating
Circuit). External gain and sense resistors allow programmability for a wide range of applications.
In the Typical Operating Circuit, PA supply current
flows from the system supply, through the external current-sense resistor (RSENSE), to the PA. The rail-to-rail
outputs of the error amplifier, A3, adjust the gain of the
PA until the voltage drop across RSENSE equals the
voltage drop across external gain resistor, RG1. The
voltage drop across RG1 sets the voltage drop across
RSENSE, with a larger voltage drop resulting in more
current delivered to the PA. The voltage drop across
RG1 is set by A1, A2, and the V-to-I FET, Q1. A voltage
applied to the PC input of the input buffer is divided by
4
four by a resistor-divider network. A2 forces its inverting
input and the source of Q1 to VPC / 4, thus setting a
voltage across RG3. The resulting current through RG3
sets the current through RG1. This unique architecture
allows the supply current to be set independent of supply voltage. Set PA supply current according to the following equation:
ICCPA = ( VPC · RG1 ) / ( 4 · RSENSE · RG3 )
Shutdown Mode
When SHDN is a logic-level low (SHDN < 0.4V), amplifiers A1, A2, and A3 are off, Q1 is turned off, and the
output of A3 is actively pulled to ground with an Nchannel FET. Supply current is reduced to less than
1µA in shutdown mode. Typical power-up time is 0.9µs
and typical power-down time is 0.3µs, using the
MAX4473 test circuit.
Applications Information
Gain Resistor Selection
(RG1, RG2, RG3)
For proper operation, do not make the value of external
gain resistors RG1 and RG2 larger than twice the value
of RG3. In most practical applications, choose RG1
smaller than RG3 to limit the voltage drop over RG1
and RSENSE. A large voltage drop over RSENSE substantially reduces the voltage applied to the PA, thus
reducing PA output power. Set RG2 equal to RG1 to
compensate for the input bias currents of A3.
Recommended values for RG3 are between 1kΩ and
10kΩ.
_______________________________________________________________________________________
Low-Cost, Low-Voltage, PA Power Control
Amplifier for GSM Applications in 8-Pin QFN
• 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
Pin Configuration
RSENSE
TOP VIEW
VCC
100Ω
0.1%
RG1
1kΩ
1%
0.1µF
VCC
PC
SHDN
GND
SR1
RG2
1kΩ
1%
SR2
MAX4473
RG3
2.5kΩ
1%
1
8
VCC
SR2
2
7
OUT
3
6
SR3
PC 4
5
GND
MAX4473
2N3904
OUT
RL
10kΩ
SR3
SR1
SHDN
CL
300pF
RE
750Ω
QFN/µMAX/SO
Chip Information
TRANSISTOR COUNT: 348
_______________________________________________________________________________________
5
MAX4473
Sense Resistor Selection (RSENSE)
Choose RSENSE based on the following criteria:
• Voltage Loss: A high R SENSE 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 currents 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.
Low-Cost, Low-Voltage, PA Power Control
Amplifier for GSM Applications in 8-Pin QFN
SOICN.EPS
8LUMAXD.EPS
MAX4473
Package Information
6 _________________________________________________________________________________________
Low-Cost, Low-Voltage, PA Power Control
Amplifier for GSM Applications in 8-Pin QFN
µ
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ______________________7
© 2002 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
MAX4473
Package Information (continued)