LT1684

Micropower Ring Tone Generator

Not Recommended for New Designs

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Overview

Features and Benefits
Product Details

Features and Benefits

This product is pending obsolescence - Contact Analog Devices for more information
Allows Dynamic Control of Output Frequency, Cadence, Amplitude and DC Offset
Active Tracking Supply Configuration Allows Linear Generation of Ring Tone Signal
No High Voltage Post-Filtering Required
Capacitive Isolation Eliminates Optocouplers
Low Distortion Output Meets International PTT Requirements
Differential Input Signal for Noise Immunity
User Adjustable Active Output Current Limit
Powered Directly From High Voltage Ringer Supply—No Additional Supplies Necessary
Supply Current: <1mA
2% Signal Amplitude Reference
Available in 14-Pin SO and DIP Packages

Product Details

The LT1684 is a telecommunication ring tone generator. The IC takes a user-generated pulse width modulated (PWM) input and converts it to a high voltage sine wave suitable for telephone ringing applications.

The LT1684 receives capacitor-isolated differential PWM input signals encoded with desired ring output cadence, frequency, and amplitude information. The LT1684 normalizes the pulse amplitude to ±1.25V for an accurate signal voltage reference. The cadence, frequency and amplitude information is extracted using a multiple-pole active filter/amplifier, producing the output ring tone signal.

The LT1684 uses its own ring tone output as a reference for generating local supply rails using complementary high voltage external MOSFETs as dynamic level-shifting devices. This 'active tracking' supply mode of operation allows linear generation of the high voltage ring tone signal, reducing the need for large high voltage filtering elements.

Applications