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
Power by Linear

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Product Lifecycle icon-recommended Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

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ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.


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The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.

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Evaluation Boards Pricing displayed is based on 1-piece.
Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.