le79r79 Zarlink Semiconductor, le79r79 Datasheet - Page 4

• Manufacturer Part Number: le79r79
• Description: Ringing Subscriber Line Interface Circuit
• Manufacturer: Zarlink Semiconductor

PRODUCT DESCRIPTION
The Legerity family of subscriber line interface circuit (SLIC) products provide the telephone interface functions required
throughout the worldwide market. Legerity SLIC devices address all major telephony markets including central office (CO), private
branch exchange (PBX), digital loop carrier (DLC), fiber-in-the-loop (FITL), radio-in-the-loop (RITL), hybrid fiber coax (HFC), and
video telephony applications.
The Legerity SLIC devices offer support of BORSHT (battery feed, overvoltage protection, ringing, supervision, hybrid, and test)
functions with features including current limiting, on-hook transmission, polarity reversal, Tip Open, and loop-current detection.
These features allow reduction of linecard cost by minimizing component count, conserving board space, and supporting
automated manufacturing.
The Legerity SLIC devices provide the two- to four-wire hybrid function, DC-loop feed, and two-wire supervision. Two-wire
termination is programmed by a scaled impedance network. Transhybrid balance can be achieved with an external balance circuit
or simply programmed using a companion Legerity codec/filter, such as the Le58QL0xx Quad SLAC (QLSLAC™) device.
The Le79R79 Ringing SLIC device is a bipolar monolithic SLIC that offers on-chip ringing. Now designers can achieve significant
cost reductions at the system level for short-loop applications by integrating the ringing function on chip. Examples of such
applications would be ISDN terminal adaptors, fiber-in-the-loop, radio-in-the-loop, hybrid fiber/coax and video telephony (home-
side) boxes. The Le79R79 Ringing SLIC can provide sufficient voltage to meet the stringent LSSGR five-ringer equivalent
specification. Using a CMOS-compatible input waveform and wave shaping R-C network, the Le79R79 Ringing SLIC can provide
trapezoidal wave ringing to meet various design requirements.
In order to further enhance the suitability of this device in short-loop, distributed switching applications, Legerity has maximized
power savings by incorporating battery switching on chip. The Le79R79 Ringing SLIC device switches between two battery
supplies such that in the off-hook (active) state, a low battery is used to save power. In order to meet the Open Circuit voltage
requirements of fax machines and maintenance termination units (MTU), the SLIC device automatically switches to a higher
voltage in the On-hook (Standby) state.
Like all of the Legerity SLIC devices, the Le79R79 Ringing SLIC device supports on-hook transmission, ring-trip detection,
programmable loop-detect threshold, and is available with on-chip polarity reversal. The Le79R79 Ringing SLIC device is a
programmable constant-current feed device with two on-chip relay drivers to operate external relays. Several performance grades
are available to meet both CCITT and LSSGR requirements, including various longitudinal balance options.
B(RING)
RTRIP1
RTRIP2
VBAT2
VBAT1
A(TIP)
HPA
HPB
Two-Wire
Interface
Switch
Driver
Figure 1. Le79R79 Block Diagram
VCC VNEG BGND
Zarlink Semiconductor Inc.
Ground-Key
Power-Feed
Ring-Trip
Off-Hook
Detector
Detector
Detector
Transmission
Controller
Signal
4
AGND/DGND
Input Decoder
and Control
Relay Driver
Relay Driver
DET
RINGIN
RYOUT2
RYOUT1
D1
D2
C1
C2
C3
RSN
RDC
RSGL
E1
RD
VTX
RDCR
RSGH
B2EN
RYE