Maxim MAX881REUB Datasheet

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General Description

The MAX881R low-noise, inverting power supply is
designed for biasing GaAsFET power amplifiers in
portable wireless applications. This device is a charge­pump inverter followed by a negative linear regulator.
The input voltage range is 2.5V to 5.5V. The output is
preset at -2.0V or can be set, using two resistors, to any
voltage from -0.5V to (-VIN+ 0.6V). It can deliver up to
4mA. The internal linear regulator also filters the output
to 1mVp-p ripple and noise.

Other features include a power-OK (POK) output that sig­nals when the negative voltage is within 7.5% of its set
point. It protects the GaAsFET by not allowing power to
be applied to the GaAsFET’s drain until it is properly
biased. The signal can be routed either to a microcon­troller or directly to a switch at the GaAsFET drain. The
MAX881R is available in a space-saving 10-pin µMAX
package.

Applications

Cell Phones
PCS Phones
PHS Phones
Wireless Handsets
Wireless Modems
Two-Way Pagers
Mobile Radios
Wireless Computers

Features

♦ Small µMAX Package
♦ 1mVp-p Output Voltage Ripple and Noise
♦ Power-OK Signal to Control GaAsFET Drain

Switch

♦ 0.05µA Logic-Controlled Shutdown
♦ 1ms Guaranteed Start-Up
♦ 2.5V to 5.5V Input
♦ -0.5V to (-V

IN

+ 0.6V) Output at up to 4mA

♦ Operates with One 4.7µF and Three 0.22µF

Capacitors (no inductors needed)

MAX881R

Low-Noise Bias Supply in µMAX

with Power-OK for GaAsFET PA

________________________________________________________________

Maxim Integrated Products

1

1
2
3
4
5

10

9
8
7
6

IN
N.C.
GND
OUTPOK

N.C. = NOT INTERNALLY CONNECTED

NEGOUT

C1-

C1+

MAX881R

µMAX

TOP VIEW

FBSHDN

Typical Operating Circuit

19-1372; Rev 1; 6/98

PART

MAX881REUB -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

10 µMAX

EVALUATION KIT

AVAILABLE

Pin Configuration

Ordering Information

ON

INPUT

2.5V TO 5.5V

OFF

OUTPUT

-2V (OR ADJ)

4mA, 1mVp-p

IN

MAX881R

SHDN
C1+

C1-

NEGOUT

FB

OUT

POK

GND

RIPPLE

CONTROLS
GaAsFET PA’s
DRAIN SWITCH

MAX881R

Low-Noise Bias Supply in µMAX
with Power-OK for GaAsFET PA

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(Circuit of Figure 3, VIN= +3.6V, FB = GND, RL= ∞, SHDN = IN, TA= -40°C to +85°C, unless otherwise noted. Typical values are at
T

A

= +25°C.) (Note 2)

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.

IN to GND.................................................................-0.3V to +6V

SHDN to GND...........................................................-0.3V to +6V

POK to GND...........................................................-0.3V to +12V

C1+ to GND.................................................-0.3V to (V

IN

+ 0.3V)

C1-, NEGOUT, OUT, FB to GND ....................-6V to (V

IN

+ 0.3V)

Continuous Power Dissipation (T

A

= +70°C)

10-Pin µMAX (derate 5.6mW/°C above +70°C)...........444mW

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range.............................-65°C to +165°C

Lead Temperature (soldering, 10sec).............................+300°C

VIN= 3V, RL= 500Ω, V

SHDN

= 0 to VIN,

POK goes low

VIN≥ 2.5V, I

OUT

= 0 to 4mA

Connected to IN or GND

VIN= 2.5V

V

IN

≥ 2.7V, I

OUT

= 0 to 4mA

VIN= 5.5V

V

POK

= 11V

I

OUT

= 4mA, circuit of Figure 3b

V

IN

≥ 2.7V, I

OUT

= 0 to 4mA

VIN≥ 2.5V, sinking 1mA

SHDN = GND

VFB= -0.5V

FB = OUT

CONDITIONS

ms1t

START

Start-Up Time

pF10C

IN

SHDN Input Capacitance

µA±1I

SHDN

SHDN Input Current

V0.35V

IL

SHDN Input Low Voltage

V2.2V

IH

SHDN Input High Voltage

µA1

POK Off Leakage Current

mV100

POK Output Level

% of

V

OUT

90 92.5 95

POK Threshold

kHz80 100 120f

OSC

Oscillator Frequency

V-(VIN- 0.6) -0.5V

OUT

Adjustable Output Voltage
Range

V-2.1 -2.0 -1.9V

OUT

V2.5 5.5V

IN

Supply Voltage Range
Preset Output Voltage

mVp-p1Output Ripple

mV/mA2 6Output Load Regulation

µA0.05 1I

SHUT

Shutdown Supply Current

V

-0.515 -0.5 -0.485

V

FB

FB Voltage

nA-10 -100FB Input Current
µA500 950I

Q

Supply Current

UNITSMIN TYP MAXSYMBOLPARAMETER

Note 1: The output may be shorted to NEGOUT or GND if the package power dissipation is not exceeded. Typical short-circuit

current is 35mA.

-0.525 -0.475

-0.535 -0.465

VIN≥ 2.5V,
I

OUT

= 0 to 4mA

TA= +25°C
TA= 0°C to +85°C
TA= -40°C to +85°C

Note 2: Specifications to -40°C are guaranteed by design, not production tested.

MAX881R

Low-Noise Bias Supply in µMAX

with Power-OK for GaAsFET PA

_______________________________________________________________________________________

3

-2.02

-1.98

-2.00

-1.94

-1.96

-1.92

1.90

-1.86

-1.88

-1.84

0 2 3 41 5 6 7 8 9 10

OUTPUT VOLTAGE

vs. OUTPUT CURRENT

MAX881R TOC01

OUTPUT CURRENT (mA)

OUTPUT VOLTAGE (V)

CIRCUIT OF FIGURE 3a

V

IN

= 2.5V

V

IN ≥

3.6V

-2.02

-1.98

-2.00

-1.92

-1.94

-1.96

-1.86

-1.88

-1.90

-1.84

0 6 82 4 10 12 14 16

OUTPUT VOLTAGE

vs. OUTPUT CURRENT

MAX881R TOC02

OUTPUT CURRENT (mA)

OUTPUT VOLTAGE (V)

CIRCUIT OF FIGURE 3b

V

IN

= 2.5V

V

IN ≥

3.6V

-2.03

-2.01

-2.02

-1.99

-2.00

-1.98

-1.97

-1.96

-1.95

2.0 3.0 3.52.5 4.0 4.5 5.0 5.5 6.0

OUTPUT VOLTAGE

vs. INPUT VOLTAGE

MAX881R TOC03

INPUT VOLTAGE (V)

OUTPUT VOLTAGE (V)

I

LOAD

= 4mA

Typical Operating Characteristics

(Circuit of Figure 3, VIN= 3.6V, TA= +25°C, unless otherwise noted.)

0

10

5

25
20
15

40
35
30

45

2.0 3.5 4.02.5 3.0 4.5 5.0 5.5 6.0

MAXIMUM OUTPUT CURRENT

vs. INPUT VOLTAGE

MAX881r TOC04

INPUT VOLTAGE (V)

OUTPUT CURRENT (mA)

V

OUT

< 2mVp-p RIPPLE

CIRCUIT OF FIGURE 3b

V

OUT

< 2mVp-p RIPPLE

CIRCUIT OF FIGURE 3a

V

OUT

≤ -1.8V

CIRCUIT OF FIGURE 3a

V

OUT

≤ -1.8V

CIRCUIT OF FIGURE 3b

0

4

8

12

16

20

24

2.0 3.02.5 3.5 4.0 4.5 5.0 5.5 6.0

MAXIMUM NEGOUT CURRENT

vs. INPUT VOLTAGE

MAX881R TOC05

INPUT VOLTAGE (V)

OUTPUT CURRENT (mA)

V

NEGOUT

= 0.9 x V

NEGOUT(NO LOAD)

CIRCUIT OF FIGURE 3b

CIRCUIT OF FIGURE 3a

300

400

500

600

700

800

900

2.0 3.02.5 3.5 4.0 4.5 5.0 5.5 6.0

NO-LOAD SUPPLY CURRENT

vs. INPUT VOLTAGE

MAX881R TOC06

INPUT VOLTAGE (V)

SUPPLY CURRENT (µA)

300

400

500

600

700

800

900

-60 -20-40 0 20 40 60 80 100

NO-LOAD SUPPLY CURRENT

vs. TEMPERATURE

MAX881R TOC07

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

VIN = 5.5V

VIN = 3.6V

VIN = 2.5V

100

300

200

500

400

700

600

800

2.0 3.0 3.52.5 4.0 4.5 5.0 5.5 6.0

START-UP TIME

vs. INPUT VOLTAGE

MAX881R TOC08

INPUT VOLTAGE (V)

START-UP TIME (µs)

CIRCUIT OF FIGURE 3a
NO LOAD
SHDN TO POK DELAY

97

98

99

100

101

102

103

2.0 3.02.5 3.5 4.0 4.5 5.0 5.5 6.0

OSCILLATOR FREQUENCY

vs. INPUT VOLTAGE

MAX881R TOC09

INPUT VOLTAGE (V)

FREQUENCY (kHz)

TA = -40°C

TA = +25°C

TA = +85°C