PBL38772/1 Ericsson, PBL38772/1 Datasheet - Page 10

• Manufacturer Part Number: PBL38772/1
• Description: Subscriber Line Interface Circuit
• Manufacturer: Ericsson

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Functional Description and Applications Information
Introduction
The Figure 8. diagram shows the PBL 387 72/1 in a typical application with a non-programmable, Combo I, codec. The
PBL 387 72/1 can equally well be used with software programmable codecs.
The component values chosen for the application diagram example yield a two-wire impedance of 600
balance resistor is calculated for a line impedance, Z
four-wire gain is set by R
applied to the two-wire input (TIP and RING). A received digital mW at the PCM receive bus results in a –3 dBm signal
level across the compromise impedance (600 ) connected at the two-wire port (TIP and RING). The gain calculations
are based on National Semiconductor combo I codec, TP 3054.
R
C
C
frequency transmission.
C
D
D
D
R
terminating impedance).
The ratio between R
R
R
R
R
R
C
V
V
TB
B
F1
TC
HP
TB
TB
B
BB
T
RX
LD
LC
REF
RT
RING
4
sets the two-wire impedance (note that R
is the ringing battery, i.e. the negative supply voltage that is used to power the SLIC, while ringing the line.
prevents reverse currents from the VB supply rail during application of negative over voltages.
, R
, C
is the talk battery supply, i.e. the negative supply voltage that sources the loop current.
is a diode that is part of the battery switching function.
sets the loop current detector threshold.
sets the constant dc loop current.
and C
and C
is normally reverse biased, but conducts supply VTB to the VBAT terminal in case the voltage VB would fail.
sets the receive gain.
sets the ring trip loop current detector threshold.
sets a SLIC reference current (must be 15.0 k , 1%, as specified).
is used for the high voltage ringing signal AGC (automatic gain control) function.
F2
B
, C
and the clamp “OVP” make up the overvoltage protection network.
RC
LP
VCC
are coupling capacitors within two SLIC feedback loops that control SLIC battery feed and SLIC voice
clamp fast transients that may bypass the OVP clamp and also filter high frequency interference (RFI filter).
are power supply bypass capacitors.
FB
and R
TX
and R
TX
PBL 387 72/1 shortform
sets the transmit gain.
FB
to produce the digital mW level at the PCM transmit bus for a signal level of +3 dBm
T
may be replaced with a complex impedance, Z
Advance Information
L
(compromise impedance), of 600
Rev. P5
Feb. 14, 2001
, resistive. The two-wire to
T
, to implement complex
, resistive. The
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