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LTC4400 - RF Power Controllers with 450kHz Loop BW and 45dB Dynamic Range

The LTC4400-1 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 temperature 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.

Features RF Power Amplifier Control in ThinSOT™ Package Internal Schottky Diode Detector with > 45dB Range Wide Input Frequency Range: 300MHz to 2.7GHz (LTC4400-1) 300MHz to 2GHz (LTC4400-2) Autozero Loop Cancels Offset Errors and Temperature Dependent Offsets Wide VCC 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: 10µA Two Pole PCTL Input Filtering Low Profile (1mm) ThinSOT (LTC4400-1) and 8-Pin MSOP (LTC4400-2) Packages Typical Application

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

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