LTC1758-1_15 Datasheet, PDF (1/16 Pages) Linear Technology – RF Power Controllers with 250kHz Control Loop Bandwidth and 40dB Dynamic Range

LTC1758-1/LTC1758-2
RF Power Controllers with
250kHz Control Loop Bandwidth and
40dB Dynamic Range
FEATURES
DESCRIPTIO
s _{Dual Band RF Power Amplifier Control (LTC1758-2)}
s _{Internal Schottky Diode Detector with Improved}
Dynamic Range vs LTC1757A
s _{Wide Input Frequency Range: 850MHz to 2GHz}
s _{Autozero Loop Cancels Offset Errors and}
Temperature Dependent Offsets
s _{Wide VIN Range: 2.7V to 6V}
Allows Direct Connection to Battery
s _{RF Output Power Set by External DAC}
s _{250kHz Control Loop Bandwidth}
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: < 1µA}
s _{Available in 8-Pin MSOP (LTC1758-1)}
and 10-Pin MSOP (LTC1758-2) Packages
s _{Pin Compatible with LTC1757A-X}
s _{Improved Start Voltage Accuracy}
s _{Improved PCTL Input Filtering}
U
APPLICATIO S
s _{Single and Dual Band GSM/GPRS Cellular Telephones}
s _{PCS Devices}
s _{Wireless Data Modems}
s _{U.S. TDMA Cellular Phones}
The LTC^®1758-2 is a dual band RF power controller for
RF power amplifiers operating in the 850MHz to 2GHz
range. The loop bandwidth reduction to 250kHz im-
proves frequency stability when controlling slow turn-on
PAs such as the Philips BGY280, Conexant RM009/
CX77302, Anadigics AWT6102/AWT6107 and the Hitachi
PF08107/PF08123B.
The LTC1758-1 is a single output RF power controller
that is identical in performance to the LTC1758-2 except
that one output (V_PCA) is provided. The LTC1758-1 can
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 < 1µA.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
LTC1758-2 Dual Band Cellular Telephone Transmitter
68Ω
V_IN ^33pF
LTC1758-2
1
10
V_IN
V_CC
Li-Ion
2
RF
9
V_PCA
3
8
SHDN
SHDN
V_PCB
4
7
BSEL
BSEL
TXEN
TXEN
5
GND
6
PCTL
900MHz
RF PA
DIRECTIONAL
COUPLER
DIPLEXER
50Ω
DAC
1.8GHz /1.9GHz
RF PA
1758 TA01
1