LTC4400-1 Datasheet, PDF (1/16 Pages) Linear Technology – RF Power Controllers with 450kHz Loop BW and 45dB Dynamic Range

LTC4400-1/LTC4400-2
RF Power Controllers with
450kHz Loop BW and
45dB Dynamic Range
FEATURES
s _{RF Power Amplifier Control in ThinSOT}^TM _Package
s _{Internal Schottky Diode Detector with > 45dB Range}
s _{Wide Input Frequency Range:}
300MHz to 2.7GHz (LTC4400-1)
300MHz to 2GHz (LTC4400-2)
s _{Autozero Loop Cancels Offset Errors and}
Temperature Dependent Offsets
s _{Wide VCC Range: 2.7V to 6V}
s _{Automatic Bandwidth Control Improves Low Power}
Ramp Response
s _{Allows Direct Connection to Battery}
s _{RF Output Power Set by External DAC}
s _{Internal Frequency Compensation}
s _{Rail-to-Rail Power Control Output}
s _{Power Control Signal Overvoltage Protection}
s _{Low Operating Current: 1mA}
s _{Low Shutdown Current: 10µA}
s _{Two Pole PCTL Input Filtering}
s _{Low Profile (1mm) ThinSOT (LTC4400-1) and}
8-Pin MSOP (LTC4400-2) Packages
U
APPLICATIO S
s _{GSM/GPRS Cellular Telephones}
s _{PCS Devices}
s _{Wireless Data Modems}
s _{U.S. TDMA Cellular Phones}
DESCRIPTIO
The LTC^®4400-1 is a SOT-23 RF power controller for fast
turn-on RF power amplifiers operating in the 300MHz to
2.7GHz range. Examples include the Hitachi PF08109B,
PF08122B, PF08123B, PF08107B and RF Micro Devices
RF3108. For slow turn-on RF power amplifiers refer to the
LTC4401-1/LTC4401-2.
RF power is controlled by driving the RF amplifier power
control pin and sensing the resultant RF output power via
a directional coupler or capacitive tap. The RF input
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 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 <10µA.
A dual control channel version (LTC4400-2) is also
available in an 8-pin MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
LTC4400-1 Dual Band Cellular Telephone Transmitter
Li-Ion
0.1µF
6
V_CC
1
RF
LTC4400-1
4
SHDN
SHDN
5
V_PCA
3
2
DAC
PCTL
GND
50Ω
BAND
SELECT
900MHz
INPUT
1.8GHz
INPUT
V_PC
900MHz
OUTPUT
PA MODULE
1.8GHz
OUTPUT
0.4pF
4400 TA01
LTC4400-1 Detector Characteristics at
900MHz and 1800MHz
10000
T_A = 25°C
V_CC = 3.6V
1000
900MHz
100
1800MHz
10
1
–26 –22 –18 –14 –10 –6 –2 2 6 10 14 18
RF INPUT POWER (dBm)
4400 TA04
sn4400 4400fas
1