le79r70 Zarlink Semiconductor, le79r70 Datasheet - Page 3

• Manufacturer Part Number: le79r70
• 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, over voltage 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 line card 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 Le79R70 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 and set top boxes. Using a CMOS-compatible input waveform and wave shaping
R-C network, the Le79R70 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 Le79R70 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 automatically switches to a higher voltage in
the On-hook (standby) state.
Like all of the Legerity SLIC devices, the Le79R70 Ringing SLIC device supports on-hook transmission, ring-trip detection and
programmable loop-detect threshold. The Le79R70 Ringing SLIC device is a programmable constant-current feed device with
two on-chip relay drivers to operate external relays. This unique device is available in the proven Legerity 75 V bipolar process.
B(RING)
RTRIP1
RTRIP2
VBAT2
VBAT1
A(TIP)
HPA
HPB
Two-Wire
Interface
Figure 1. Le79R70 Block Diagram
Switch
Driver
Zarlink Semiconductor Inc.
VCC VNEG
Ground-Key
Ring-Trip
Off-Hook
Transmission
Detector
Detector
Detector
Power-Feed
Controller
Signal
3
BGND
AGND/DGND
Input Decoder
and Control
Relay
Driver
Relay
Driver
E1
RINGIN
RYOUT2
RYE
RYOUT1
D1
D2
C1
C2
C3
DET
RD
VTX
RSN
RDC
RDCR
RSGL
RSGH
B2EN