L3030 STMicroelectronics, L3030 Datasheet - Page 9

• Manufacturer Part Number: L3030
• Description: SUBSCRIBER LINE INTERFACE KIT
• Manufacturer: STMicroelectronics

stem ; in this case the internal dropout voltage is
equal to 30V.
Fig. 3 shows the DC characteristic in boost battery
condition.
In conversationmode, on request of controlproces-
sor, whatever condition is set (normal or boost bat-
tery, direct or reverse polarity), you can inject the
12kHz(or16kHz)signal (permanentlyapplied at the
pin 33 with 950mVrms typ. amplitude), as metering
pulses. A patented automatic control system adjust
the level of the metering signal, across the line, to
2Vrms setting BIT3 = 0, or to 5Vrms setting BIT3 =
1 ; this, regardless of the line impedance. Moreover
the metering signal is ramped at the beginningand
at the end of each pulse to prevent undesirableclic-
king noise ; the slope is determined by the value of
CINT (see the external component list of L3030).
The SLIC also provides, in the transmit direction
(fromline to 4-wire side), an amplifier to insert anex-
ternal notch filter (series resonator) for suppressing
the 12/16kHz residual signal.
Fig. 4 shows a suggestednotch Filter configuration.
The metering pulses can be injected with a DC line
current equal to zero (ON-HOOK Operation).
If teletax is not used the notch filter can be replaced
by a 1K resistor.
Inconversationmode theAC impedanceatthe lineter-
minals,ZML,issynthetizedbytheexternalcomponents
ZAC and RP, according to the following formula :
Dependingon the characteristic of the ZAC network,
ZML canbe eithera pure resistance or a complex im-
pedance,soallowing ST SLICtomeetdifferentstand-
ards as far as the return loss is concerned. The
capacitorCCOMP guaranteesstability to the system.
The two-to-four wire conversion is achieved by me-
ans of a Wheatstone bridge configuration,the sides
Figure 4 : ExternalTeletaxe Filter.
f
L
2
R2 x
1
LxC
R3
R4
ZML = ZAC + (RP1 + RP2)
x
R5
xC2
Figure 3 : DC Characteristic (b.b.)
of which being :
1) the line impedance (Zline),
2) the SLIC impedance at line terminals (ZML),
3) thenetworkZA connectedbetweenpin 36and 41
4) the network ZB between pin 36 and ground that
For a perfectbalancing,the following equationshall
be verified :
It is important to underline that ZA and ZB are not
obliged to be equal to ZML and to Zline, but they
both may be multiplied by a factor (up to ten) so al-
lowing use of smaller capacitors.
Inconversation,the L3000Sdissipatesabout250mW
foritsownoperation; thedissipationdependingonthe
current supplied to the line shall be added.
The fig 5 and fig 6 show the DC characteristicfor two
different Feeding resistance.
2 x 200 Ohm and 2 x 400 respectively.
of L3030 (see externalcomponentlist of L3030),
shall copy the line impedance.
I
LIM
= 25/30/45/70mA.
ZA
ZB
Zline
ZML
L3000S - L3030
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