Le75183
1.0
Product Description
Data Sheet
The Le75183A/B/C Line Card Access Switch is a monolithic solid-state device providing the equivalent switching
functionality of three 2 form C switches. The Le75183 is designed to provide power ringing access, line test access
(test out), and SLIC test access (test in) to tip and ring in central office, digital loop carrier, private branch exchange,
digitally added main line, and hybrid fiber coax/fiber-in-the-loop analog line card applications. An additional pair of
solid-state contacts are also available to provide access for testing of the ringing generator.
The Le75183A/B has seven states: the idle talk state (line break switches closed, all other switches open), the
power ringing state (ringing access switches closed, all other switches open), loop access (test out) state (loop
access (test out) switches closed, all other switches open), SLIC test state (test in switches closed, all other
switches open), simultaneous loop and SLIC access state (loop and test in switches closed, all others open),
ringing generator test state (ring test switches closed, all others open), and an all OFF state. The seven states in
the Le75183A/B are also in the Le75183C, with an additional simultaneous test-out and ring-test state, making the
Le75183C appropriate for digital loop carrier and other Telcordia TR-57 applications.
The Le75183 offers break-before-make or make-before-break switching, with simple logic level input control.
Because of the solid-state construction, voltage transients generated when switching into an inductive ringing lead
during ring cadence or ring trip are minimized, possibly eliminating the need for external zero cross switching
circuitry. State control is via logic level inputs, so no additional driver circuitry is required.
The line break switch is a linear switch that has exceptionally low ON-resistance and an excellent ON-resistance
matching characteristic. The ringing access switch has a breakdown voltage rating >480 V which is sufficiently high,
with proper protection, to prevent breakdown in the presence of a transient fault condition (i.e., passing the
transient on to the ringing generator).
Incorporated into the Le75183A and Le75183C is a diode bridge/SCR clamping circuit, current-limiting circuitry, and
a thermal shutdown mechanism to provide protection to the SLIC device and subsequent circuitry during fault
conditions. This is shown in block diagram as version A/C. Positive and negative lightning is reduced by the
current-limiting circuitry and steered to ground via diodes and the integrated SCR. Power cross is also reduced by
the current-limiting and thermal shutdown circuits.
The Le75183B version provides only an integrated diode bridge along with current limiting and thermal shutdown
(see block diagram for version B). This will cause positive faults to be directed to ground and negative faults to
battery. In either polarity, faults are reduced by the current-limit and/or thermal shutdown mechanisms.
To protect the Le75183 from an overvoltage fault condition, use of a secondary protector is required. The
secondary protector must limit the voltage seen at the tip/ring terminals to prevent the breakdown voltage of the
switches from being exceeded. To minimize stress on the solid-state contacts, use of a foldback- or crowbar- type
secondary protector is recommended. With proper choice of secondary protection, a line card using the Le75183
will meet all relevant ITU-T, LSSGR, FCC, or UL* protection requirements.
The Le75183 operates off of a 5 V supply only. This gives the device extremely low idle and active power
dissipation and allows use with virtually any range of battery voltage. This makes the Le75183 especially
appropriate for remote power applications such as DAML or FOC/FITL or other Telcordia TA 909 applications
where power dissipation is particularly critical.
A battery voltage is also used by the Le75183, only as a reference for the integrated protection circuit. The Le75183
will enter an all OFF state upon loss of battery.
During power ringing, to turn on and maintain the ON state, the ring access switch and ring test switch will draw a
nominal 2 mA from the ring generator.
The default power up state of Le75183 is in all OFF state, unless otherwise being overwritten by external controls.
The Le75183 device is packaged in a 20-pin, plastic SOIC (GULL) (Le75183ADSC/BDSC/CDSC), a 32-pin QFN
(Le75183AFQC/BFQC/CFQC), and a 28-pin, plastic SOIC (GULL) (Le75183AFSC/BFSC/CZFSC). The 28-pin
package is available to support existing designs. For new designs, it may be advantageous to use the other two
smaller size packages.
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Zarlink Semiconductor Inc.
ZARLINK [ ZARLINK SEMICONDUCTOR INC ]
