L7583A Datasheet, PDF (13/20 Pages) Agere Systems – Line Card Access Switch

Data Sheet
February 2001
L7583A/B/C/D Line Card Access Switch
Protection (continued)
Integrated SLIC Protection (continued)
External Secondary Protector
With the above integrated protection features, only one
overvoltage secondary protection device on the loop
side of the L7583 is required. The purpose of this
device is to limit fault voltages seen by the L7583 so as
not to exceed the breakdown voltage or input-output
isolation rating of the device. To minimize stress on the
L7583, use of a foldback- or crowbar-type device is rec-
ommended. A detailed explanation and design equa-
tions on the choice of the external secondary protection
device are given in the An Introduction to L758X Series
of Line Card Access Switches Application Note. Basic
design equations governing the choice of external sec-
ondary protector are given below.
s |VBATmax| + |Vbreakovermax| < |Vbreakdownmin(break)|
s |Vringingpeakmax| + |VBATmax| + |Vbreakovermax| <
|Vbreakdownmin(ring)|
s |Vringingpeakmax| + |VBATmax| < |Vbreakovermin|
where:
VBATmax—Maximum magnitude of battery voltage.
Vbreakovermax—Maximum magnitude breakover voltage
of external secondary protector.
Vbreakovermin—Minimum magnitude breakover voltage
of external secondary protector.
Vbreakdownmin(break)—Minimum magnitude breakdown
voltage of L7583 break switch.
Vbreakdownmin(ring)—Minimum magnitude breakdown
voltage of L7583 ring access switch.
Vringingpeakmax—Maximum magnitude peak voltage of
ringing signal.
Series current-limiting fused resistors or PTCs should
be chosen so as not to exceed the current rating of the
external secondary protector. Refer to the manufac-
turer’s data sheet for requirements.
Table 15. Electrical Specifications, Protection Circuitry
Parameters Related to Diodes (in Diode Bridge)
Parameter
Test Condition
Measure
Min
Typ
Voltage Drop @ Continuous Cur- Apply ±dc current limit Forward
—
—
rent (50 Hz/60 Hz)
of break switches Voltage
Voltage Drop @ Surge
Current
Apply ±dynamic cur- Forward
—
5
rent limit of break
Voltage
switches
Parameters Related to Protection SCR
Surge Current
Gate Trigger Current*^†
—
—
—
—
—
—
—
25
Gate Trigger Current^† Tempera-
—
ture Coefficient
—
—
–0.5
Hold Current
—
—
70
—
Gate Trigger Voltage
Trigger current
—
VBAT – 4 —
Reverse Leakage Current
ON-State Voltage^§
VBAT
—
0.5 A, t = 0.5 µs
VON
2.0 A, t = 0.5 µs
—
—
—
—
–3
—
–5
Max
3
—
‡
50
—
—
VBAT – 2
1.0
—
—
Unit
V
V
A
mA
%/°C
mA
V
µA
V
V
* Previous versions of this data sheet specified a Trigger Current of 50 mA minimum. Trigger Current is defined as the minimum current drawn
from tip and ring to turn on the SCR. The specification in this data sheet is Gate Trigger Current, which is defined as the maximum current
that can flow into the battery before the SCR turns on.
† Typical at 25 °C.
‡ Twice ± dynamic current limit of break switches.
§ In some instances, the typical ON-state voltage can range as low as –25 V.
Lucent Technologies Inc.
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