LTC4400

Obsolete

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

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Overview

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 V_CC 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

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.

Applications