LTC4401-1

` RF Power Amplifier Control in ThinSOT<sup>TM</sup> Package
` Internal Schottky Diode Detector with >45dB Range
` Wide Input Frequency Range:
     800MHz to 2.7GHz (LTC4401-1)
     800MHz to 2GHz (LTC4401-2)
` Autozero Loop Cancels Offset Errors and Temperature Dependent Offsets
` Wide V<sub>CC</sub> Range: 2.7V to 6V
` Automatic Bandwidth Control Improves Low Power Ramp Response
` Allows Direct Connection to Battery
` RF Output Power Set by External DAC
` Internal Frequency Compensation
` Rail-to-Rail Power Control Output
` Power Control Signal Overvoltage Protection
` Low Operating Current: 1mA
` Low Shutdown Current: 10A
` Two Pole PCTL Input Filtering
` Low Profile (1mm) ThinSOT (LTC4401-1) and 8-Pin MSOP (LTC4401-2) Packages

· GSM/GPRS Cellular Telephones
· PCS Devices
· Wireless Data Modems
· U.S. TDMA Cellular Phones

V_CC to GND ................................................... 0.3V to 6.5V
V_PCA/B Voltage to GND ................................. 0.3V to 3.2V
PCTL Voltage to GND ....................... 0.3V to (V_CC + 0.3V)
RF Voltage to GND ................................. (V_CC 2.6V) to 7V
BSEL, SHDN Voltage to GND ............ 0.3V to (V_CC + 0.3V)
I_VPCA/B ....................................................................... 10mA
Operating Temperature Range (Note 2) .. 30°C to 85°C
Storage Temperature Range .................. 65°C to 150°C
Maximum Junction Temperature ............................... 125°C
Lead Temperature (Soldering, 10 sec)...................... 300°C

The LTC^®4401-1 is a SOT-23 RF power controller for slow turn-on RF power amplifiers operating in the 800MHz to 2.7GHz range. The loop bandwidth is set at 250kHz to improve frequency stability when controlling slow turn-on RF power amplifiers such as the Conexant CX77301/CX77302, CX77304, CX77314, Anadigics AWT6107 and the RF Micro Devices RF3160.

RF power of LTC4401-1 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 power control pin voltages.

Internal and external offsets are cancelled over temperature by an autozero control loop, allowing accurate low power programming. The shutdown feature disables the part and reduces the supply current to <10A.

A dual control channel version (LTC4401-2) is also available in an 8-pin MSOP package.