Description
General
This electronic subscriber loop interface circuit (SLIC) is optimized for low cost and low power consumption while providing a full-feature set.
Included in the feature set is quiet reverse battery. Quiet polarity reversal is possible because the ac path is uninterrupted during transmission. The dc loop current limit is user-adjustable via a single external resistor. The maximum battery voltage is specified as –65 V for long loop applications. The L8567 supports on-hook transmission.

Features
■ Low active power (typical 149 mW during on-hook transmission)
■ Sleep state for low idle power (47 mW typical)
■ Quiet tip/ring polarity reversal
■ Distortion-free on-hook transmission
■ –35 V to –65 V battery operation
■ Convenient operating states:
    — Forward active
    — Polarity reversal active
    — Sleep
    — Forward disconnect
■ Supervision functions:
    — Fixed threshold off-hook detector with longitudinal rejection and hysteresis
    — Ring trip detector
    — Thermal shutdown indication
■ Adjustable loop current limit
■ Three driver outputs for relay driver
■ LED driver output to indicate off-hook
■ Latched parallel data interface
■ Battery and +5 V required:
    — Optional auxiliary lower voltage battery to reduce short loop power
■ –40 °C to +85 °C operational temperature range
■ User-selectable power management techniques
■ Thermal protection
■ 32-pin PLCC or 44-pin PLCC packaging