L8560 Datasheet, PDF (1/46 Pages) Agere Systems – Low-Power SLIC with Ringing

Data Sheet
April 2000
L8560 Low-Power SLIC with Ringing
Features
Description
s Full-feature set for central office applications
s Also ideal for ISDN terminal adapters, pair gain,
and cable telephony applications
s Auxiliary input for second battery, and internal
switch to enable its use to save power in short tele-
phone loops
s 5 V only operation or optional ±5 V operation for
reduced power consumption
s Low active power (85 mW typical) and scan power
(61 mW typical) with 5 V only operation
s Low active power (68 mW typical with auxiliary bat-
tery) and scan power (45 mW typical) with ±5 V
operation
s Quiet tip/ring polarity reversal
s Per-line ringing available for short loops
s Reduced overhead and increased current limit dur-
ing ring mode for lower-battery operation or
increased ring loop length
s Supports meter pulse injection
s Distortion-free full duplex from 0 mA dc loop cur-
rent on-hook transmission
s Convenient operating states:
— Forward powerup
— Polarity reversal powerup
— Forward sleep
— Ground start
— Disconnect
s Adjustable supervision functions:
— Off-hook detector with longitudinal rejection
— Ground key detector with longitudinal rejection
— Ring trip detector
s Independent, adjustable dc and ac parameters:
— dc feed resistance (44-pin PLCC version)
— Loop current limit
— Termination impedance
s Thermal protection
The L8560 full-feature, low-power subscriber line
interface circuit (SLIC) is optimized for low power
consumption while providing an extensive set of fea-
tures. This part is ideal for ISDN terminal adapter
applications and short-loop, power-sensitive applica-
tions such as pair gain and cable telephony. This part
is also designed for PBX, DLC, or CO applications.
The SLIC includes an auxiliary battery input and a
battery switch. In short-loop applications, SLICs can
be used in high battery to present a high on-hook
voltage, and then switched to low battery to reduce
off-hook power.
To help minimize the required auxiliary battery volt-
age, the dc feed resistance and overhead voltage are
set at 55 Ω and 6.7 V, respectively. This allows an
undistorted on-hook transmission of a 3.14 dBm sig-
nal into a 900 Ω loop impedance.
The device offers the reverse battery function. Using
the reverse battery, the device can provide a bal-
anced power ring signal to tip and ring. In this
mode of operation, the battery switch is used to
apply a high-voltage battery during ringing and a
lower-voltage battery during the talk and idle states.
Also included in the L8560 is a dc current-limit
switch, which increases the dc current limit during
power ringing. In addition, dc overhead voltage is
reduced during the ring state. With the battery and
current-limit switches, and overhead reduction, the
L8560 can provide sufficient power to ring a true
North American 5 REN load of 1386 Ω + 40 µF.
The device offers ring trip and loop closure supervi-
sion with 0.3 V and 2 mA hysteresis, respectively. It
also includes the ground start state and ring ground
detection. A summing node for meter pulse injection
to 2.2 Vrms is also included. The 44-pin PLCC ver-
sion also has a spare uncommitted op amp, which
may be used for ac gain setting or meter pulse filter-
ing.