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.


  • Wireless Local Loop Telephones
  • Key System/PBX Equipment
  • Fiber to the Curb Telecom Equipment

Product Lifecycle icon-not-recommended Not Recommended for New Designs

This designates products ADI does not recommend broadly for new designs.

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