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 charge-

pump 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 (-V

+ 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 sig-

nals 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 microcon-

troller or directly to a switch at the GaAsFET drain. The

MAX881R is available in a 10-pin µMAX package.

Applications

Cell Phones Wireless Modems

PCS Phones Two-Way Pagers

PHS Phones Mobile Radios

Wireless Handsets 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 Startup

♦ 2.5V to 5.5V Input

♦ -0.5V to (-V

+ 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

N.C.

GND

OUTPOK

N.C. = NOT INTERNALLY CONNECTED

NEGOUT

C1-

C1+

MAX881R

µMAX

TOP VIEW

FBSHDN

MAX881R

OUT

POK

C1+

C1-

NEGOUT

GND

SHDN

CONTROLS

GaAsFET PA’s

DRAIN SWITCH

OUTPUT

-2V (OR ADJ)

4mA, 1mVp-p

RIPPLE

INPUT

2.5V TO 5.5V

OFF

Typical Operating Circuit

19-1372; Rev 2; 1/04

PART

MAX881REUB -40°C to +85°C

TEMP RANGE PIN-PACKAGE

10 µMAX

Pin Configuration

Ordering Information

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.

EVALUATION KIT

AVAILABLE

Summary of content (8 pages)

PAGE 1
9-1372; Rev 2; 1/04 KIT ATION EVALU LE B A IL A AV Low-Noise Bias Supply in µMAX with Power-OK for GaAsFET PA 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.
PAGE 2
MAX881R Low-Noise Bias Supply in µMAX with Power-OK for GaAsFET PA ABSOLUTE MAXIMUM RATINGS 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 (VIN + 0.3V) C1-, NEGOUT, OUT, FB to GND ....................-6V to (VIN + 0.
PAGE 3
Low-Noise Bias Supply in µMAX with Power-OK for GaAsFET PA 1.90 -1.92 -1.94 VIN = 2.5V -2.00 -1.90 -1.92 -1.96 1 2 3 4 5 6 7 8 9 -1.98 -1.99 -2.00 -2.02 2 4 6 8 10 12 14 2.0 16 2.5 3.0 3.5 4.0 4.5 5.0 5.5 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) INPUT VOLTAGE (V) MAXIMUM OUTPUT CURRENT vs. INPUT VOLTAGE MAXIMUM NEGOUT CURRENT vs. INPUT VOLTAGE NO-LOAD SUPPLY CURRENT vs.
PAGE 4
Typical Operating Characteristics (continued) (Circuit of Figure 3, VIN = 3.6V, TA = +25°C, unless otherwise noted.) OUTPUT NOISE AND RIPPLE (CIRCUIT OF FIGURE 3a) STARTUP FROM SHUTDOWN (NO LOAD) 0 VOUT 0 -2V POK MAX881R-TOC12 VIN = 3.6V VOUT = -2V IOUT = 2.
PAGE 5
Low-Noise Bias Supply in µMAX with Power-OK for GaAsFET PA PIN NAME 1 C1+ Positive Terminal for C1 FUNCTION 2 C1- Negative Terminal for C1 3 NEGOUT 4 POK 5 SHDN Active-Low, Logic-Level Shutdown Input. Connect to IN for normal operation. Do not leave this pin unconnected. 6 FB Dual-Mode™ Feedback Input. When FB is connected to GND, the output is preset to -2V. To select other voltages, connect FB to an external resistor-divider (Figure 4). Do not leave this pin unconnected.
PAGE 6
MAX881R Low-Noise Bias Supply in µMAX with Power-OK for GaAsFET PA TO PA GATE BIAS OUT VIN VCC FOR POWER AMPLIFIER C3 0.22µF C1+ C4 MAX881R P POK IN OUT C1 0.22µF 100k OFF Detailed Description The applied input voltage (VIN) is inverted to a negative voltage at NEGOUT by a capacitive charge pump. This voltage is regulated by an internal linear regulator at OUT (Figure 1). With FB connected to GND, VOUT is regulated at -2V.
PAGE 7
Low-Noise Bias Supply in µMAX with Power-OK for GaAsFET PA C3 0.22µF IN C1+ C1 0.22µF OFF C2 0.22µF R2 MAX881R C1- ON OUT C4 4.7µF FB SHDN NEGOUT POK regulating, the output resistance of the circuit is simply the linear-regulator load regulation (2mV/mA). C1, C2, and C3 should be 0.22µF capacitors with less than 0.4Ω ESR. C4 should be a 4.7µF capacitor with less than 0.1Ω ESR.
PAGE 8
Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) e 10LUMAX.EPS MAX881R Low-Noise Bias Supply in µMAX with Power-OK for GaAsFET PA 4X S 10 10 INCHES H 0 0.50±0.1 0.6±0.1 1 1 0.6±0.1 BOTTOM VIEW TOP VIEW D2 MILLIMETERS MAX DIM MIN 0.043 A 0.006 A1 0.002 A2 0.030 0.037 0.120 D1 0.116 0.118 0.114 D2 0.116 0.120 E1 0.118 E2 0.114 0.199 H 0.187 L 0.0157 0.