Features

• OBSOLETE:  For Information Purposes Only.  Contact Linear Technology for Potential Replacement.
• Generates 5V Varactor Drive from a 3V Supply
• Wide Supply Voltage Range: 2.7V to 6V
• Requires Only Three External Components
• Micropower Operation: 400µA at 3V Supply
• Shutdown Mode Drops Supply Current Below 1µA
• Low Output Noise: 15µV_RMS
• Amplifier Gain: 2.3
• Up to 500kHz Signal Bandwidth
• MS8 and SO-8 Packages
• Very Low Input Bias Current: 10nA Max
• Amplifier Offset Maintains Phase Detector in Linear Region

Typical Application

Description

OBSOLETE:  For Information Purposes Only.  Contact Linear Technology for Potential Replacement.

The LTC1340 is a varactor diode driver designed to generate 5V varactor drive from a single 3V or higher voltage supply. It includes a low noise amplifier with an internal gain of 2.3 and a self-contained charge pump to generate output voltages above the input supply. The amplifier input stage includes a built-in offset voltage that allows the output voltage to swing to ground without requiring OV on the input. This feature maintains the phase detector within its linear range of operation. The LTC1340 requires only three external surface mount capacitors to implement a complete varactor driver module.

The LTC1340 features output referred noise of 15µV_RMS, minimizing frequency deviation in PLL frequency synthesizer systems. Supply current is 400µA typically with a 3V supply, and drops to 1µA in shutdown, maximizing operating life in battery-powered systems. Amplifier bandwidth is user-adjustable from 10kHz up to 500kHz and the output typically sinks or sources 20µA, allowing fast output signal changes with a typical varactor load. The amplifier input features rail-to-rail input common mode range, allowing it to interface with the output of virtually any phase detector circuit.

The LTC1340 is available in MS8 and SO-8 packages.