CPC7582_1 Datasheet, PDF (14/19 Pages) Clare, Inc. – Line Card Access Switch

CPC7582
the CPC7582 switches when pulled to a logic low.
Although logically disabled, if the ringing switch (SW4)
is active (closed), it will remain closed until the next
current zero crossing event.
As shown in the table “Break-Before-Make Operation
for all Version (Ringing to Talk Transition)” on page 14,
this operation is similar to the one shown in
“Break-Before-Make Operation - All Versions” on
page 13, except in the method used to select the all off
state, and in when the IN_RINGING and IN_TEST inputs
are reconfigured for the talk state.
1. Pull T_SD to a logic low to end the ringing state.
This opens the ringing return switch (SW3) and
prevents any other switches from closing.
2. Keep T_SD low for at least one-half the duration of
the ringing cycle period to allow sufficient time for
a zero crossing current event to occur and for the
circuit to enter the break before make state.
3. During the T_SD low period, set the IN_RINGING and
IN_TEST inputs to the talk state (0, 0).
4. Release T_SD, allowing the internal pull-up to
activate the break switches.
When using T_SD as an input, the two recommended
states are 0 (overrides logic input pins and forces an
all off state) and float (allows switch control via logic
input pins and the thermal shutdown mechanism is
active). This requires the use of an open-collector type
buffer.
Forcing T_SD to a logic high disables the thermal
shutdown circuit and is therefore not recommended as
this could lead to device damage or destruction in the
presence of excessive tip or ring potentials.
2.2.6 Break-Before-Make Operation for all Version (Ringing to Talk Transition)
State
Ringing
All-Off
Break-
Before-
Make
Talk
IN_RINGING
1
0
0
0
IN_TEST LATCH T_SD
Timing
Ringing
Break Return
Switches Switch
(SW3)
Ringing
Switch
(SW4)
Test
Switches
0
Floating
-
Off
On
On
Off
Hold this state for at least one-half of the
0
ringing cycle. SW4 waiting for zero
Off
Off
On
Off
current to turn off.
0
0
0
SW4 has opened
Off
Off
Off
Off
0
Floating
Close Break Switches
On
Off
Off
Off
2.3 Data Latch
The CPC7582 has an integrated data latch. The latch
operation is controlled by logic-level input pin 11
(LATCH). The data input of the latch is pin 10
(IN_RINGING) and pin 9 (IN_TEST) of the device while the
output of the data latch is an internal node used for
state control. When LATCH control pin is at logic 0, the
data latch is transparent and data control signals flow
directly through to state control. A change in input will
be reflected in the switch state. When LATCH control
pin is at logic 1, the data latch is active and a change
in input control will not affect switch state. The
switches will remain in the position they were in when
the LATCH changed from logic 0 to logic 1 and will not
respond to changes in input as long as the latch is at
logic 1. The T_SD input is not tied to the data latch.
Therefore, T_SD is not affected by the LATCH input and
the T_SD input will override state control.
2.4 Thermal Shutdown
Setting T_SD to +5 V allows switch control using the
logic inputs. This setting, however, also disables the
thermal shutdown circuit and is therefore not
recommended. When using logic controls via the input
pins, pin 7 (T_SD) should be allowed to float. As a
result, the two recommended states when using pin 7
(T_SD) as a control are 0, which forces the device to the
all-off state, or float, which allows logic inputs to
remain active. This requires the use of an
open-collector type buffer.
2.5 Ringing Switch Zero-Cross Current Turn Off
After the application of a logic input to turn SW4 off,
the ringing switch is designed to delay the change in
state until the next zero-crossing. Once on, the switch
requires a zero-current cross to turn off, and therefore
should not be used to switch a pure DC signal. The
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