CPC7583_12 Datasheet, PDF (14/19 Pages) IXYS Corporation – Line Card Access Switch

INTEGRATED CIRCUITS DIVISION
2. Functional Description
2.1 Introduction
The CPC7583 has the following states:
• Talk. Loop break switches SW1, and SW2 closed, all
other switches open.
• Ringing. Ringing switches SW3, SW4 closed, all
other switches open.
• TESTout. Testout switches SW5, SW6 closed, all
other switches open.
• Ringing generator test. SW7, SW8 closed, all
other switches open.
• TESTin. Testin switches SW9 and SW10 closed.
• Simultaneous TESTin and TESTout. SW9, SW10,
SW5, and SW6 closed, all other switches open.
• Simultaneous test out and ringing generator
test. SW5, SW6, SW7, and SW8 closed, all other
switches open (only on the xC and xD versions).
• All Off. All switches open.
See “Truth Tables” on page 12 for more information.
The CPC7583 offers break-before-make and
make-before-break switching from the ringing state to
the talk state with simple logic level input control.
Solid-state switch construction means no impulse
noise is generated when switching during ringing
cadence or ring trip, eliminating the need for external
zero-cross switching circuitry. State-control is via
logic-level input so no additional driver circuitry is
required. The linear line break switches SW1 and
SW2 have exceptionally low R_ON and excellent
matching characteristics. The ringing switch SW4 has
a minimum open contact breakdown voltage of 465 V.
This 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).
Integrated into the CPC7583 is an over voltage
clamping circuit, active current limiting, and a thermal
shutdown mechanism to provide protection to the
SLIC device during a fault condition. Positive and
negative surges are reduced by the current limiting
circuitry and hazardous potentials are diverted to
ground via diodes and the integrated SCR.
Power-cross potentials are also reduced by the current
limiting and thermal shutdown circuits.
CPC7583
To protect the CPC7583 from an overvoltage fault
condition, the use of a secondary protector is required.
The secondary protector must limit the voltage seen at
the T_LINE and R_LINE terminals to a level below the
maximum breakdown voltage of the switches. To
minimize the stress on the solid-state contacts, use of
a foldback or crowbar type secondary protector is
recommended. With proper selection of the secondary
protector, a line card using the CPC7583 will meet all
relevant ITU, LSSGR, TIA/EIA and IEC protection
requirements.
The CPC7583 operates from a +5 V supply only. This
gives the device extremely low idle and active power
consumption and allows use with virtually any range of
battery voltage. The battery voltage is also used by the
CPC7583 as a reference for the integrated protection
circuit. In the event of a loss of battery voltage, the
CPC7583 enters the all-off state.
2.2 Switch Logic
The CPC7583 provides, when switching from the
ringing state to the talk state, the ability to control the
release timing of the ringing switches SW3 and SW4
relative to the state of the loop break switches SW1
and SW2 using simple logic-level input. This is
referred to as a make-before-break or
break-before-make operation. When the line break
switch contacts (SW1 and SW2) are closed (or made)
before the ringing access switch contacts (SW3 and
SW4) are opened (broken), this is referred to as
make-before-break operation. Break-before-make
operation occurs when the ringing access contacts
(SW3 and SW4) are opened (broken) before the line
break switch contacts (SW1 and SW2) are closed
(made). With the CPC7583, the make-before-break
and break-before-make operations can easily be
selected by applying the proper sequence of logic
inputs to IN_TESTout, IN_RINGING, and IN_TESTin.
The logic sequences for either mode of operation are
given in “Make-Before-Break Operation (Ringing to Talk
Transition)” on page 15 and “Break-Before-Make Operation
(Ringing to Talk Transition)” on page 15. Logic states and
explanations are given in “Truth Tables” on page 12.
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