1

LTC1957-1/LTC1957-2

Single/Dual Band RF Power

Controllers with 40dB Dynamic Range

The LTC

power amplifiers operating in the 850MHz to 2GHz range.

The input voltage range is optimized for operation from

a single lithium-ion cell or 3

× NiMH. Several functions

required for RF power control and protection are inte-

grated in one small 10-pin MSOP package, thereby

minimizing PCB area.

The LTC1957-1 is a single output RF power controller

that is identical in performance to the LTC1957-2 except

be used to drive a single RF or dual channel module with

integral multiplexer. This part is available in an 8-pin

MSOP package.

RF power is controlled by driving the RF amplifier power

control pins and sensing the resultant RF output power

via a directional coupler. The RF sense voltage is peak

detected using an on-chip Schottky diode. This detected

voltage is compared to the DAC voltage at the PCTL pin

to control the output power. The RF power amplifier is

protected against high supply current and high power

control pin voltages.

Internal and external offsets are cancelled over tempera-

ture by an autozero control loop, allowing accurate low

power programming. The shutdown feature disables the

part and reduces the supply current to < 1

µA.

s

Dual Band RF Power Amplifier Control (LTC1957-2)

s

Internal Schottky Diode Detector with Improved

Dynamic Range vs the LTC1757A

s

Wide Input Frequency Range: 850MHz to 2GHz

s

Autozero Loop Cancels Offset Errors and

Temperature Dependent Offsets

s

s

Allows Direct Connection to Battery

s

RF Output Power Set by External DAC

s

Fast Acquire After Transmit Enable

s

Internal Frequency Compensation

s

Rail-to-Rail Power Control Outputs

s

Power Control Signal Overvoltage Protection

s

Low Operating Current: 1mA

s

Very Low Shutdown Current: < 1

µA

s

Available in a 8-Pin MSOP Package (LTC1957-1)

and 10-Pin MSOP (LTC1957-2)

s

Pin Compatible with the LTC1757A-X

s

Improved Start Voltage Accuracy and Range

s

Improved PCTL Input Filtering

, LTC and LT are registered trademarks of Linear Technology Corporation.

RF

SHDN

BSEL

GND

10

9

8

7

6

1

2

3

4

5

TXEN

PCTL

LTC1957-2

33pF

68

Ω

Li-Ion

SHDN

BSEL

TXEN

900MHz

DAC

RF PA

DIRECTIONAL

COUPLER

DIPLEXER

1.8GHz /1.9GHz

RF PA

50

Ω

1957 TA01

LTC1957-2 Dual Band Cellular Telephone Transmitter

s

Single and Dual Band GSM/GPRS Cellular Telephones

s

PCS Devices

s

Wireless Data Modems

s

U.S. TDMA Cellular Phones

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

DESCRIPTIO