Final Electrical Specifications
LTC1757A-1/LTC1757A-2
Single/Dual Band
RF Power Controllers
FEATURES
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DESCRIPTIO
April 2000
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Dual Band RF Power Amplifier Control (LTC1757A-2)
Improved Internal Schottky Diode Detector
Wide Input Frequency Range: 850MHz to 2GHz
Autozero Cancels Initial Offsets and Temperature
Dependent Offset Errors
Wide V
IN
Range of 2.7V to 6V Allows
Direct Connection to Battery
RF Output Power Set by External DAC
Fast Acquire After Transmit Enable
Internal Frequency Compensation
Rail-to-Rail Power Control Outputs
RF PA Supply Current Limiting
Battery Overvoltage Protection
Power Control Signal Overvoltage Protection
Low Operating Current: 1mA
Very Low Shutdown Current: < 1µA
Available in a 8-Pin MSOP Package (LTC1757A-1)
and 10-Pin MSOP (LTC1757A-2)
The LTC
®
1757A-2 is a dual band RF power controller for
RF power amplifiers operating in the 850MHz to 2GHz
range. The LTC1757A is pin compatible with the LTC1757
but has improved RF detection 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 integrated in one small 10-pin
MSOP package, thereby minimizing PCB area.
The LTC1757A-1 is a single output RF power controller
that is identical in performance to the LTC1757A-2 except
that one output (V
PCA
) is provided. The LTC1757A-1 can
be used to drive a single RF channel 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 voltage and 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 < 1µA.
APPLICATIO S
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Single and Dual Band GSM Cellular Telephones
PCS Devices
Wireless Data Modems
TDMA Cellular Telephones
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
68Ω
V
IN
33pF
Li-Ion
SHDN
BSEL
LTC1757A-2 Dual Band Cellular Telephone Transmitter
LTC1757A-2
1
2
3
4
5
V
IN
RF
SHDN
BSEL
GND
V
CC
V
PCA
V
PCB
TXEN
PCTL
10
9
8
7
6
900MHz
TXEN
RF PA
DIRECTIONAL
COUPLER
DIPLEXER
DAC
1.8GHz /1.9GHz
RF PA
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
U
50Ω
1757A TA01
U
U
1
LINER [ LINEAR TECHNOLOGY ]
