LT1684 Datasheet | Linear Technology

LT1684 Micropower Ring Tone Generator Features s s DESCRIPTIO s s s s s s s s s 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: < 1m A 2% Signal Amplitude Reference Available in 14-Pin SO and DIP Packages The LT®1684 is a telemunication 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 multiplepole 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 plementary 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. , LTC and LT are registered trademarks of Linear Technology Corporation. U APPLICATIO S s s s Wireless Local Loop Telephones Key System/PBX Equipment Fiber to the Curb Tele Equipment TYPICAL APPLICATIO PWM CONTROLLER P1 µC P2 DC ISOLATION 100p F Electrically Isolated Ring Tone Generator 100V 6.8n F IN A 10k IN B LT1684 LIM + OUT ATREF P1 GATE + FB1 V+ 1N4001 100k 100Ω IRF610 10k 100p...