Data Sheet
April 2000
L8560 Low-Power SLIC with Ringing
Features
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Description
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.
Full-feature set for central office applications
Also ideal for ISDN terminal adapters, pair gain,
and cable telephony applications
Auxiliary input for second battery, and internal
switch to enable its use to save power in short tele-
phone loops
5 V only operation or optional ±5 V operation for
reduced power consumption
Low active power (85 mW typical) and scan power
(61 mW typical) with 5 V only operation
Low active power (68 mW typical with auxiliary bat-
tery) and scan power (45 mW typical) with ±5 V
operation
Quiet tip/ring polarity reversal
Per-line ringing available for short loops
Reduced overhead and increased current limit dur-
ing ring mode for lower-battery operation or
increased ring loop length
Supports meter pulse injection
Distortion-free full duplex from 0 mA dc loop cur-
rent on-hook transmission
Convenient operating states:
— Forward powerup
— Polarity reversal powerup
— Forward sleep
— Ground start
— Disconnect
Adjustable supervision functions:
— Off-hook detector with longitudinal rejection
— Ground key detector with longitudinal rejection
— Ring trip detector
Independent, adjustable dc and ac parameters:
— dc feed resistance (44-pin PLCC version)
— Loop current limit
— Termination impedance
Thermal protection
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AGERE [ AGERE SYSTEMS ]
