LT1684 Datasheet, PDF (1/16 Pages) Linear Technology – Micropower Ring Tone Generator

LT1684
Micropower
Ring Tone Generator
FEATURES
s _{Allows Dynamic Control of Output Frequency,}
Cadence, Amplitude and DC Offset
s _{Active Tracking Supply Configuration Allows Linear}
Generation of Ring Tone Signal
s _{No High Voltage Post-Filtering Required}
s _{Capacitive Isolation Eliminates Optocouplers}
s _{Low Distortion Output Meets International}
PTT Requirements
s _{Differential Input Signal for Noise Immunity}
s _{User Adjustable Active Output Current Limit}
s _{Powered Directly From High Voltage Ringer}
Supply—No Additional Supplies Necessary
s _{Supply Current: < 1mA}
s _{2% Signal Amplitude Reference}
s _{Available in 14-Pin SO and DIP Packages}
U
APPLICATIO S
s _{Wireless Local Loop Telephones}
s _{Key System/PBX Equipment}
s _{Fiber to the Curb Telecom Equipment}
DESCRIPTIO
The LT^®1684 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 nor-
malizes 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
Electrically Isolated Ring Tone Generator
DC
PWM
ISOLATION
CONTROLLER
100pF
10k
P1
µC
100pF
10k
P2
IN A
GATE⁺
IN B
V⁺
LT1684
LIM⁺
OUT
BG_OUT
AT_REF
COMP1
FB1
100pF
6.8nF 100k
100Ω
1N4001
3k
20pF
2k
5k
COMP2
AMPIN
LIM^–
300k
4700pF
V^–
GATE^–
1µF
1N5817
100Ω
6.8nF 100k
IRF610
100V
+
RING TONE
OUTPUT
0.1µF
–
( ) ^±100mA
CAPABILITY
IRF9610
–100V
FB1: FERRONICS FMB1601
[phone]
1684 TA01
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