Analog Line Cards
Off-Hook (SLIC) Protection
Off-hook protection is accomplished by choosing a SIDACtor device that meets the
following criteria to ensure proper coordination between the supply voltage (VREF) and the
maximum voltage rating of the SLIC to be protected.
V
DRM > VREF
VSꢀ?ꢀVSLIC Breakdown
This criterion can be accomplished in a variety of different ways. For applications using an
external ring generator and a fixed battery voltage, two P0641S_ SIDACtor devices
(P0721S_, P0901S_, or P1101S_ depending on the value of VREF) are used — one Tip to
Ground, one Ring to Ground. For applications using a ring-generating SLIC such as AMD’s
Am79R79, the B1XX0C_ or B1XX1U_ can be used.
IPP Selection
The I of the SIDACtor device must be greater than or equal to the maximum available
PP
surge current (IPK(available)) of the applicable regulatory requirements. Calculate the maximum
available surge current by dividing the peak surge voltage supplied by the voltage generator
(VPK) by the total circuit resistance (RTOTAL). The total circuit resistance is determined by
adding the source resistance (RS) of the surge generator to the series resistance in front of
the SIDACtor device on Tip and Ring (RTIP and RRING).
IPPꢀOꢀIPK(available)
IPK(available) = VPK / RTOTAL
For metallic surges:
R
TOTAL = RS + RTIP + RRING
For longitudinal surges:
TOTAL = RS + RTIP
R
RTOTAL = RS + RRING
Reference Diagrams
Figure 3.21 shows the use of Teccor’s “SC” rated SIDACtor devices and the F1250T
TeleLink fuse to meet the surge immunity requirements of GR 1089. Teccor’s P1200SC and
P2000SC, specifically designed to protect Agere Systems (formerly Lucent
Microelectronics) Line Card Access Switch (LCAS), provide on-hook protection. Two
P0641SCs provide off-hook protection. Any additional series resistance is absent because
the “C” series SIDACtor device and F1250T TeleLink fuse are designed to withstand
GR 1089 surges without the aid of additional components such as line feed resistors and
PTCs.
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© 2002 Teccor Electronics
SIDACtor Data Book and Design Guide
®
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