Datasheet MAX4473ESA, MAX4473EUA Datasheet (Maxim)

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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 deliv­ered 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-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 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 com­promising 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

♦ 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

Low-Cost, Low-Voltage, PA Power Control

Amplifier for GSM Applications in 8-Pin µMAX

________________________________________________________________

Maxim Integrated Products

1

GND

PC

0.1µF

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

V

CC

V

CC

V

CC

R

SENSE

RG1 RG2

I

CCPA

MAX4473

4 · RG3 · R

SENSE

V

PC

· RG1

I

CCPA

=

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.

MAX4473

Low-Cost, Low-Voltage, PA Power Control
Amplifier for GSM Applications in 8-Pin µMAX

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= +2.7V to +6.5V, SHDN > +2.4V, MAX4473 test circuit, RG1 = RG2 = 1kΩ ±1%, RG3 = 2.5kΩ ±1%, R

SENSE

= 100Ω ±1%, R

L

= 10kΩ, CL= 300pF, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= +6.0V, VPC= +1.0V, TA= +25°C.)

(Note 1)

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.

VCCto GND ...........................................................................+7V

SR1, SR2, SR3, PC, SHDN,

OUT to GND............................................-0.3V to (V

CC

+ 0.3V)

SR1 to SR3......................................................................0 to V

CC

OUT and SR3 Short-Circuit Duration

to V

CC

or GND ........................................................Continuous

Current into Any Pin..........................................................±50mA

Continuous Power Dissipation (T

A

= +70°C)

µMAX (derate 4.10mW/°C above +70°C) .....................330mW

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, 10sec).............................+300°C

V

OUT

= VCC/ 2

RL= 500Ω
to V

CC

/ 2

VPC= 0

2.7V < V

CC

< 6.5V, VPC= GND

1V < V

SR1

, V

SR2

< VCC,

VPC= GND

Inferred from CMRR test; VPC= GND (Note 2)

1V < V

SR1

, V

SR2

< V

CC

SHDN < 0.4V, V

SR1

= V

SR2

= V

CC

1V < V

SR1

, V

SR2

< V

CC

SHDN < 0.4V, RL= 10kΩ

1V < V

SR1

, V

SR2

< VCC, VPC= GND,

SR3 = unconnected

SHDN = 0 to V

CC

1V < V

SR1

, V

SR2

< VCC, VPC= GND,

SR3 = unconnected

CONDITIONS

mA20Output Current Limit

0.15 V

CC

-

0.15

80 120

80 130

80 125

dB

80 130

dB80 90Power-Supply Rejection Ratio

75 95

65 85

Common-Mode Rejection Ratio

µA±0.001 ±0.5SR1, SR2 Shutdown Leakage Current

µA±0.001 ±0.2SR1, SR2 Input Bias Offset Current

µA±0.04 ±1SR1, SR2 Input Bias Current

mA1.2 2Supply Current

V2.7 6.5Supply Voltage

V1V

CC

SR1, SR2 Input Common-Mode
Voltage Range

µV/°C

10SR1, SR2 Input Offset Voltage Drift

mV±0.5 ±2SR1, SR2 Input Offset Voltage

µA0.03 1Shutdown Supply Current

V2.4

SHDN Input High Voltage

V0.4

SHDN Input Low Voltage

µA±0.5

SHDN Input Current

UNITSMIN TYP MAXPARAMETER

VCC= 2.7V
VCC= 6.5V

VCC= 6.5V, 0.3V < V

OUT

< 6V

VCC= 2.7V, 0.3V < V

OUT

< 2.4V

RL= 10kΩ
to VCC/ 2

VCC= 6.5V, 0.7V < V

OUT

< 5.5V

VCC= 2.7V, 0.7V < V

OUT

< 2.2V

RL= 10kΩ, CL= 300pF

RL= 10kΩ, CL= 300pF, fo= 10kHz

degrees60Phase Margin

MHz

2Gain-Bandwidth Product

Measured from 30% to 70% of V

OUT

, RL= 10kΩ,

CL= 300pF

V/µs

1.8Slew Rate

Large Signal-Gain

RL= 10kΩ to VCC/ 2
RL= 500Ω to VCC/ 2

V

0.5 V

CC

-

0.5

Output Voltage Swing

dB

ERROR AMPLIFIER

GENERAL

MAX4473

Low-Cost, Low-Voltage, PA Power Control

Amplifier for GSM Applications in 8-Pin µMAX

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +2.7V to +6.5V, SHDN > +2.4V, MAX4473 test circuit, RG1 = RG2 = 1kΩ ±1%, RG3 = 2.5kΩ ±1%, R

SENSE

= 100Ω ±1%, R

L

= 10kΩ, CL= 300pF, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= +6.0V, VPC= +1.0V, TA= +25°C.)

(Note 1)

Note 1: Limits over temperature are guaranteed by design.
Note 2: No output phase-reversal for input common-mode voltage range from GND to V

CC

. 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.

VPC= 2.55V, SR1 = SR2 = V

CC

GND < VPC< VCC- 0.15V

No sustained oscillations (Note 3)

Measure voltage across RG1, 0.3V < VPC< 2.55V (Note 4)
Bandwidth from VPCto V

RG1

CONDITIONS

mA0.750 4SR3 Output Current Limit

µA±0.04 ±1

pF0 300Capacitive Load Stability

PC Input Bias Current

V/V0.095 0.1 0.105VPCto V

RG1

Ratio

MHz2PC Input Bandwidth

UNITSMIN TYP MAXPARAMETER

Typical Operating Characteristics

(See

Test Circuit

, TA= +25°C, unless otherwise noted.)

0.4

0.6

1.0

0.8

1.2

1.4

2.5 3.5 4.03.0 4.5 5.0 5.5 6.0 6.5

SUPPLY CURRENT vs. SUPPLY VOLTAGE

MAX4473 toc01

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

TA = -40°C

TA = +25°C

TA = +85°C

SHDN = V

CC

PC = GND

0.0900

0.0925

0.0950

0.0975

0.1000

0.1025

0.1050

0.1075

0.1100

021 3456

V

RG1

/ VPC RATIO vs. VPC RESPONSE

MAX4473 toc02

VPC (V)

V

RG1

/ V

PC

(V/V)

VCC = 6.0V

70 0

-30
10 100 1k 10k 100k 1M

10M

ERROR-AMPLIFIER RESPONSE

-10

0

-20

MAX4473 toc03

FREQUENCY

GAIN (dB)

PHASE (degrees)

10

20

30

40

50

60

-180

-144

-126

-162

-108

-90

-72

-54

-36

-18

PHASE

GAIN

A

VCL

= 1000

V

CC

= 6.5V

V

CM

= V

CC

/ 2

V

PC

= 0

100k

ERROR
AMPLIFIER

100Ω

10k

300pF

OUT

500mV/div

SHDN

2V/div

ENABLE/DISABLE TIME

MAX4473 toc04

500ns/div

VCC = 6.5V
V

PC

= 2V

GND

GND

0

0.10

0.05

0.20

0.15

0.25

0.30

-40 10-15 35 60 85

ERROR-AMPLIFIER

OUTPUT LOW VOLTAGE vs. TEMPERATURE

MAX4473 toc05

TEMPERATURE (°C)

V

OL

(V)

VCC = 6.5V, RL = 10kΩ to V

CC

/ 2

VCC = 2.7V, RL = 10kΩ to V

CC

/ 2

VCC = 6.5V, RL = 500Ω to V

CC

/ 2

VCC = 2.7V, RL = 500Ω to V

CC

/ 2

0.15

0.10

0.05
0

0.25

0.20

0.35

0.30

0.40

0.45

-40 10-15 35 60 85

ERROR-AMPLIFIER

OUTPUT HIGH VOLTAGE vs. TEMPERATURE

MAX4473 toc06

TEMPERATURE (°C)

V

CC

-

V

OH

(V)

VCC = 2.7V, RL = 10kΩ to V

CC

/ 2

VCC = 6.5V, RL = 500Ω to V

CC

/ 2

VCC = 6.5V, RL = 10kΩ to V

CC

/ 2

VCC = 2.7V, RL = 500Ω to V

CC

/ 2

From 50% of SHDN edge to V

OUT

= 1V, VPC= 2V

µs0.9 1.5Enable/Disable Time

GAIN CONTROL BUFFER AND V-TO-I CONVERTER

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 pro-

grammability 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 (R

SENSE

), to the PA. The rail-to-rail
outputs of the error amplifier, A3, adjust the gain of the
PA until the voltage drop across R

SENSE

equals the
voltage drop across external gain resistor, RG1. The
voltage drop across RG1 sets the voltage drop across
R

SENSE

, 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

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:

I

CCPA

= ( VPC· RG1 ) / ( 4 · R

SENSE

· 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 R

SENSE

. A large voltage drop over R

SENSE

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.

MAX4473

Low-Cost, Low-Voltage, PA Power Control
Amplifier for GSM Applications in 8-Pin µMAX

4 _______________________________________________________________________________________

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, R

SENSE

, through gain resistor RG1.

2 SR2

Noninverting Input of Error Amplifier. Connect to load side of current-sense resistor, R

SENSE

, through gain

resistor RG2. Set RG2 equal to RG1.

PIN

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 V

CC

for nor-

mal operation.

4 PC Power Control Input. Apply a voltage to PC to set a DC current through the sense resistor to control PA bias.

8 V

CC

+2.7V to +6.5V Voltage Supply Input. Bypass to ground with a 0.1µF capacitor.

7 OUT Output of Error Amplifier. Connect to gain control pin of power amplifier in bias control applications.

6 SR3

Inverting Input of V-to-I Converter and Source of V-to-I FET, Q1. Connect to ground through gain resistor
RG3.

5 GND Ground

Pin Description

Sense Resistor Selection (R

SENSE

)

Choose R

SENSE

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 R

SENSE

values.

• Accuracy: A high R

SENSE

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
R

SENSE

to provide approximately 100mV of sense

voltage for the full-scale current in each application.

• Efficiency and Power Dissipation: At high current
levels, the I

2

R losses in R

SENSE

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.

MAX4473

Low-Cost, Low-Voltage, PA Power Control

Amplifier for GSM Applications in 8-Pin µMAX

_______________________________________________________________________________________ 5

_________________________Test Circuit

2N3904

SR1

GND

R

SENSE

SR2

OUT

SR3

PC

SHDN

V

CC

V

CC

C

L

300pF

R

L

10k

RG1
1k
1%

RG2
1k
1%

RG3

2.5k
1%

100Ω

0.1%

0.1µF

MAX4473

R

E

750Ω

Pin Configuration

SR3

GNDPC

1
2

87V

CC

OUTSR2

SR1

µMAX/SO

TOP VIEW

3

4

6

5

MAX4473

SHDN

Chip Information

TRANSISTOR COUNT: 348

MAX4473

Low-Cost, Low-Voltage, PA Power Control
Amplifier for GSM Applications in 8-Pin µMAX

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.

6

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© 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

Package Information

SOICN.EPS

8LUMAXD.EPS