The MAX774 ISDN ring-tone power-supply (IRG) evaluation
kit (EV kit) provides the high voltages required for
implementing a plain old telephone system (POTS) interface
on ISDN modems and line cards. It is a fully assembled
and tested board that provides a tightly regulated,
-24V output for powering off-hook voice communication
and a -70V output for on-hook, ring-tone generation.
The EV kit is designed for applications that implement
the telephone interface using subscriber line interface
circuit (SLIC) ICs, such as the AM79R79 from AMD and
comparable products from Lucent, Harris, and other
vendors. Its design feeds back the -24V output, achieving
tight regulation for clean voice-signal transmission.
An economical, off-the-shelf, surface-mount transformer
reduces system cost and size. Compact design conserves
board area. High efficiency and reduced quiescent
current make this design the optimal solution for
green PC and portable designs.
The MAX774 IRG EV kit can also be used to evaluate
the MAX775/MAX776. It has a layout that allows modification
for -48V output operation as well as adaptation
for lower-voltage European applications.
Key Features
Applications/Uses
+3V to +16.5V Operating Range
Tightly Regulated, -24V Output for Off-Hook
Voice Communication
-70V Output Supports a Five-Ringer-Equivalent
Load (VIN > 10.5V)
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