June 1999
PBL 386 50/2
Subscriber Line
Interface Circuit
Description
The PBL 386 50/2 Subscriber Line Interface Circuit (SLIC) is a 90 V bipolar integrated
circuit for use in Central Office Metering applications and other telecommunications
equipment. The PBL 386 50/2 has been optimized for low total line interface cost and
a high degree of flexibility in different applications.
The PBL 386 50/2 emulates resistive loop feed, programmable between 2x50
Ω
and 2x900
Ω,
with short loop current limiting adjustable to max 45 mA. In the current
limited region the loop feed is nearly constant current with a slight slope
corresponding to 2x30kΩ.
A second, lower battery voltage may be connected to the device to reduce short
loop power dissipation. The SLIC automatically switches between the two battery
supply voltages without need for external components or external control.
The SLIC incorporates loop current, ground key and ring trip detection functions.
The PBL 386 50/2 is compatible with both loop and ground start signaling.
Two- to four-wire and four- to two-wire voice frequency (VF) signal conversion is
accomplished by the SLIC in conjunction with either a conventional CODEC/filter or
with a programmable CODEC/filter, e.g. SLAC, SiCoFi, Combo II. The programmable
two-wire impedance, complex or real, is set by a simple external network.
Longitudinal voltages are suppressed by a feedback loop in the SLIC and the
longitudinal balance specifications meet Bellcore TR909 requirements.
The PBL 386 50/2 package options are 24-pin SSOP, 24-pin SOIC or 28-pin PLCC.
Key Features
• 24-pin SSOP package
• Programmable two-wire signal
headroom for 2.2 V
rms
metering
• High and low battery with automatic
switching
• Only +5 V feed in addition to battery
• Selectable transmit gain (0.5x or 0.25x)
• 70 mW on-hook power dissipation in
active state
• On-hook transmission
• Long loop battery feed tracks Vbat for
maximum line voltage
• No power-up sequence
• 43V open loop voltage @
-48V battery feed
• Constant loop voltage for line leakage
<5 mA (RLeak ~ >10 kΩ @ -48V)
• Full longitudinal current capability
during on-hook state
• Analog over temperature protection
permits transmission while the
protection circuit is active
• Line voltage measurement
Ring Relay
Driver
RRLY
• Polarity reversal
• Ground key detector
• Tip open state with ring ground
detector
DT
DR
TIPX
RINGX
HP
Ring Trip
Comparator
Input
Decoder
and
Control
C1
C2
C3
DET
Ground Key
Detector
VCC
P
B
L
LP
PLD
REF
VTX
VBAT2
VBAT
Off-hook
Detector
38
PBL
6 50
/2
AGND
BGND
VF Signal
Transmission
RSN
PTG
24-pin SOIC, 24-pin SSOP, 28-pin PLCC
Figure 1. Block diagram.
1
38 PB
6 L
50
/2
Two-wire
Interface
Line Feed
Controller
and
Longitudinal
Signal
Suppression
POV
PSG
PLC
38
6
50
/2
ERICSSON [ ERICSSON ]
