General Description

The MAX1958/MAX1959 power amplifier (PA) power-

management ICs (PMICs) integrate an 800mA, dynami-

cally adjustable step-down converter, a 5mA Rail-to-

temperature sensor to power a heterojunction bipolar

transistor (HBT) PA in W-CDMA and N-CDMA cell

phones.

The high-efficiency, pulse-width modulated (PWM), DC-

to-DC buck converter is optimized to provide a guaran-

teed output current of 800mA. The output voltage is

dynamically controlled to produce any fixed-output volt-

age in the range of 0.75V to 3.4V (MAX1958) or 1V to

3.6V (MAX1959), with settling time less than 30µs for a

full-scale change in voltage and current. The 1MHz PWM

switching frequency allows the use of small external

components while pulse-skip mode reduces quiescent

current to 190µA with light loads. The converter utilizes a

low on-resistance internal MOSFET switch and synchro-

nous rectifier to maximize efficiency and minimize

external component count. The 100% duty-cycle opera-

tion allows for an IC dropout voltage of only 130mV (typ)

at 600mA load.

The micropower op amp is used to provide bias to the

HBT PA to maximize efficiency. The amplifier features

active discharge in shutdown for full PA bias control. It

has 5mA rail-to-rail drive capability, 800kHz gain-band-

width product, and 120dB open-loop voltage gain.

The precision temperature sensor measures tempera-

tures between -40°C to +125°C, with linear tempera-

ture-to-voltage analog output characteristics.

5mm thin QFN package (0.8mm max height).

Applications

W-CDMA and N-CDMA Cellular Phones

Wireless PDAs and Modems

Features

o Step-Down Converter

Dynamically Adjustable Output Voltage from

0.75V to 3.4V (MAX1958)

Dynamically Adjustable Output Voltage from

1V to 3.6V (MAX1959)

800mA Guaranteed Output Current

130mV IC Dropout at 600mA Load

Low Quiescent Current

190µA (typ) in Skip Mode (MAX1958)

3mA (typ) in PWM Mode

0.1µA (typ) in Shutdown Mode

1MHz Fixed-Frequency PWM operation

16% to 100% Duty-Cycle Operation

No External Schottky Diode Required

Soft-Start

o Operational Amplifier

5mA Rail-to-Rail Output

Active Discharge in Shutdown

800kHz Gain-Bandwidth Product

Ω)

o Temperature Sensor

Accurate Sensor -11.7mV/°C Slope

-40°C to +125°C-Rated Temperature Range

W-CDMA/N-CDMA Cellular Phone HBT PA

Management ICs

________________________________________________________________ Maxim Integrated Products

1

13

12

11

14

15

LX

IN

INP

PWM

PGND

4

3

2

1

TOUT

AGND

SHDN2

AOUT

5

REF

MAX1958/

MAX1959

TOP VIEW

THIN QFN

5mm x 5mm

Pin Configuration

Ordering Information

19-2659; Rev 0; 10/02

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.

PART

TEMP RANGE

PIN-PACKAGE

MAX1958ETP

-40

°C to +85°C

20 Thin QFN-EP*

MAX1959ETP

-40

°C to +85°C

20 Thin QFN-EP

Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.

Typical Operating Circuit and Functional Diagram appear at

end of data sheet.

EVALUATION

KIT

AVAILABLE

*EP = Exposed paddle.