參數(shù)資料
型號(hào)： L7597
廠商： Lineage Power
英文描述： Resistive Subscriber Line Interface Circuit (SLIC), Ring Relay, and Protector (SRP) for Short Loop and TA-909 Applications(用于短環(huán)路和TA-909的電阻性用戶線接口、振鈴繼電器和保護(hù)器)
中文描述： 電阻用戶線接口電路（SLIC），環(huán)繼電器和保護(hù)（SRP）的短環(huán)路和TA - 909應(yīng)用（用于短環(huán)路和電訊- 909的電阻性用戶線接口，振鈴繼電器和保護(hù)器）
文件頁(yè)數(shù)： 18/34頁(yè)
文件大小： 564K
代理商： L7597
18
Lucent Technologies Inc.
Advance Data Sheet
March 1997
Relay, and Protector (SRP) for Short Loop and TA-909 Applications
L7597 Resistive Subscriber Line Interface Circuit (SLIC), Ring
Applications
General
The L7597 supplies a precise differential current to the
Tip/Ring pair (via PT and PR) as a function of analog
signals on IRCV and RCVN. However, the current driv-
ers connected to PT and PR are not designed to supply
dc feed current to the loop. The dc loop current is fed by
two external 200
resistors. When a loop is idle (on
hook), the battery switch (SW1) is turned on to connect
the Ring lead to V
BATH
which is typically –48 V; thus
providing sufficient Tip/Ring open circuit voltage to
operate various types of customer premises equipment
(CPE). Transmission may or may not be enabled in the
idle dc feed condition. If transmission is enabled (on-
hook transmission), the current drivers are biased to a
preset dc current (10 mA into PR and 5 mA out of PT)
so that they can both source and sink sufficient signal
current when no dc loop current is flowing (even in the
presence of longitudinal currents on Tip and Ring).
When the loop is off hook, the battery switch (SW1) is
turned off and the current limiter becomes active. This
connects the Ring lead to V
BATL
(typically –25.5 V)
through an accurate current-limiter circuit which saves
off-hook power dissipation. Transmission is enabled in
this dc feed condition, but the dc bias current in the
drivers is turned off (hence, no increased power dissi-
pation) because dc loop current is flowing.
The external 200
dc feed resistors will, for the most
part, determine the longitudinal balance of the SLIC;
thus, they must be matched appropriately to meet the
longitudinal balance requirements (0.35% for 50 dB
balance). The impedance of the battery switch and cur-
rent limiter in series with the Ring-side dc feed resistor
is reduced by the battery noise cancellation circuit so
that it has minimal effect on the longitudinal balance.
The dc feed resistors also have a significant impact on
the termination impedance of the SLIC. Some feed-
back, using external components, allows the user to
adjust the termination impedance somewhat from the
400
dc feed resistance so that the primary applica-
tion of the L7597 is for a 600
Ring resistive termina-
tion. Because the L7597 does not supply dc feed
current to the loop, outputs PT and PR can be coupled
to the Tip and Ring through a sufficiently high resis-
tance to allow for simple lightning protection of the driv-
ers. However, the resistance must be low enough to
achieve the coupling of sufficient ac signal to the Tip
and Ring from the available power supply. Since the Tip
and Ring drivers are current sources, the value of this
resistance does not affect the performance of the SLIC
and is somewhat arbitrary. The value chosen is typi-
cally 1000
.
The L7597 also senses the differential Tip/Ring voltage
via sense inputs TS and RS. The differential dc voltage
is used internally for switchhook detection. The detec-
tor threshold is preset internally. The differential Tip/
Ring ac signal appears on analog output XMT. Also
included on the L7597 are three SCR protectors, a
relay driver, one logic output (indicates switchhook and
ring trip status), a 4-bit parallel logic interface, a ringing
access switch, a ring trip detector, and a circuit which
eliminates the battery noise that is coupled to the Tip
and Ring through the dc feed resistors.
The following diagram and table shows the basic exter-
nal components required with the L7597 SLIC. Specific
component values are given in cases where the value
is fixed. In cases where the value may change (i.e.,
components that determine the ac interface), the value
is not listed but equations to determine these values
are given later in this document.
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