LT1684 - Micropower Ring Tone Generator


  • This product is pending obsolescence - contact Linear Technology 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

Typical Application

LT1684 Typical Application


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.


CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.

For complete and up to date package information and drawings, please refer to our packaging page

Part Number Package Code Temp Package
LT1684CN#PBF N-14 N C 05-08-1510 (N14) Yes
LT1684CS#PBF SO-14 S C 05-08-1610 (S14) Yes
LT1684CS#TRPBF SO-14 S C 05-08-1610 (S14) Yes
LT1684IN#PBF N-14 N I 05-08-1510 (N14) Yes
LT1684IS#PBF SO-14 S I 05-08-1610 (S14) Yes
LT1684IS#TRPBF SO-14 S I 05-08-1610 (S14) Yes

LT1684 Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
  • Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number Package Temp Price
LT1684CN#PBF N-14 C $4.35 $3.65 Yes
LT1684CS#PBF SO-14 C $4.50 $3.75 Yes
LT1684CS#TRPBF SO-14 C $3.81 Yes
LT1684IN#PBF N-14 I $5.20 $4.35 Yes
LT1684IS#PBF SO-14 I $5.35 $4.45 Yes
LT1684IS#TRPBF SO-14 I $4.51 Yes
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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 Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC192A LT1684CS | TELCOM Ring Tone Generator, +5Vin, 20-REN Output $100.00
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Click here to view our complete list of demo boards


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

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