le75282 Zarlink Semiconductor, le75282 Datasheet - Page 3

• Manufacturer Part Number: le75282
• Description: Dual Intelligent Line Card Access Switch
• Manufacturer: Zarlink Semiconductor

PRODUCT DESCRIPTION
The Le75282 Dual LCAS device has six operating states:
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Control is provided by an Intelligent Subscriber Line Audio-processing Circuit (ISLAC), such as the Le79228 codec, or any
microcontroller. See
The Le75282 Dual LCAS device 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 load 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 > 320 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 Le75282 Dual LCAS device is a diode bridge, current-limiting circuitry, and a thermal shutdown mechanism
to provide protection to the SLIC device and subsequent circuitry during fault conditions. Positive faults are directed to ground
and negative faults to battery. In either polarity, faults are reduced by the built-in current-limit and/or thermal shutdown
mechanisms.
To protect the Le75282 Dual LCAS device from an overvoltage fault condition, use of a secondary protector is required. The
secondary protector must limit the voltage seen at the A (Tip)/B (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 Le75282 device will meet all relevant ITU-T,
LSSGR, FCC, or UL protection requirements.
The Le75282 Dual LCAS device provides extremely low idle and active power dissipation and allows use with virtually any range
of battery voltage. This makes the Le75282 Dual LCAS device especially appropriate for remote power applications such as
DAML or FOC/FITL or other Bellcore TA 909 applications where power dissipation is particularly critical.
Battery voltage is monitored by the control circuitry and used as a reference for the integrated protection circuit. The Le75282
device will enter an All Off state upon loss of battery.
During ringing, to turn on and maintain the ON state, the ringing access switch will draw a nominal 2 mA from the ring generator.
The Le75282 Dual LCAS device is packaged in a 44-pin TQFP package.
Idle/Talk
Ringing
Test
Test/Monitor
Test Ringing
All Off
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Test access switches closed, line break and ringing access switches open.
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Line break and ringing and test access switches open.
Ringing access switches closed, line break and test access switches open.
Line break switches closed, ringing and test access switches open.
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Test access and line break switches closed, ringing access switches open.
Applications, on page 14
Test and ringing access switches closed, line break switches open.
for proper connection of the control bus (P-bus).
Zarlink Semiconductor Inc.
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