LUCL8567AAU-D AGERE [Agere Systems], LUCL8567AAU-D Datasheet - Page 21

• Manufacturer Part Number: LUCL8567AAU-D
• Description: SLIC for Peoples Republic of China Applications
• Manufacturer: AGERE [Agere Systems]

Data Sheet
August 1999
Functional Description
General
The L8567 is a full-feature subscriber loop interface cir-
cuit (SLIC) designed to provide the battery feed and
supervision functions to the tip/ring pair. The device
uses a current sense/voltage feed architecture. That is,
the device senses tip/ring current and supplies a pre-
cise voltage that is proportional to the tip/ring current at
the VTX output. The overall transconductance (tip/ring
current to VTX voltage gain) is set by a single external
resistor, R
The device feeds a precise differential voltage to tip
and ring as a function of the signal voltages at the
RCVN and RCVP inputs. The codec output is con-
nected to the RCVN/RCVP SLIC inputs.
Use with T7507 Codec for Use in People’s
Republic of China
The L8567 SLIC and Lucent T7507 codec together
form a matched device set designed to meet the spe-
cific MPT (Ministry of Post and Telecom) requirements
for telephony in the People’s Republic of China. The ac
interface between the L8567 and the T7507 codec is
extremely simple, requiring only a single dc blocking
capacitor in the transmit direction, and a short-circuit
connection between the codec and SLIC inputs RCVN
and RCVP .
The T7507 codec has a fixed digital transmit gain stage
and two digital gain stages in the receive direction. The
choice of gain in the receive direction is user-selectable
via a bit in the serial logic input bit stream. The transmit
gain of the T7507 codec is such that when the tip/ring
to VTX transconductance of the L8567 SLIC is set to
39.75 V/A (R
transmit gain is 0 dB into 813
equivalent resistance of the PRC complex impedance
network of 200
receive gains of the T7507 codec are such that the
overall PCM to tip/ring receive gain is user-selectable
to either –3.5 dB or –7.0 dB into 813
Lucent Technologies Inc.
TG
. The voltage at VTX is fed to the codec.
TG
= 7.87 k ), the overall tip/ring to PCM
+ 680
||
100 nF at 1000 Hz.) The
. (Note that 813
.
is the
Note also that the T7507 codec will digitally synthesize
a termination impedance of 200
order to do this, the codec will assume use of 50
series protection resistors, plus the resistance of the
L758X Lucent solid-state switch on both tip and ring. If
the L758X switch is not used, the return loss perfor-
mance will degrade slightly; however, it will still meet
MPT standards. Gain flatness will not be affected; how-
ever, gain levels will shift less than 0.2 dB. To compen-
sate (if desired), the resistance of the series protection
resistor should be increased approximately 20 , to
account for the resistance of the switch.
Hybrid cancellation is also done digitally by the T7507
codec, assuming a complex hybrid balance network of
200
The T7507 codec operates off of a single 5 V power
supply. Thus, a line card using the L8567 SLIC and
T7507 codec does not require a –5 V supply. Since the
T7507 is a 5 V only device, the analog input and output
of the T7507 is referenced to 2.5 V. However, the
dynamic input range of the L8567 SLIC is high enough
to accommodate ac signals referenced to 2.5 V, thus
eliminating the need for an external dc blocking capaci-
tor in the receive direction. The basic loop start sche-
matic, using an L8567 SLIC, T7507 codec, and L7583
switch, for PRC termination, is shown in Figure 20.
The control logic interface of the L8567 SLIC is
matched to the control logic of the T7507. The latched
control inputs of the L8567 are designed to be driven
by the T7507 control data outputs. The gated supervi-
sion outputs of the L8567 SLIC are designed to feed
data inputs to the T7507 codec. The T7507 codec sup-
plies the required EN pulses to the L8567 SLIC. Con-
trol data to the L8567 and supervision from the L8567
is received from, and passed to, the microcontroller at
the serial data interface in the T7507 codec. See the
T7507 data sheet for additional details.
People’s Republic of China Applications
+ 680
||
100 nF.
+ 680
L8567 SLIC for
||
100 nF. In
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