CPC7593 Datasheet, PDF (17/24 Pages) Clare, Inc. – Line Card Access Switch

CPC7593
2.3.4 Make-Before-Break Operation Logic Table (Ringing to Talk Transition)
State IN_RINGING IN_TESTin IN_TESTout Latch
Ringing
1
0
0
Make-
Before-
0
0
0
0
Break
Talk
0
0
0
T_SD
Timing
Break
Switches
Ringing
Return
Switch
(SW3)
Ringing
Switch
(SW4)
Test
Switches
-
Off
On
On
Off
SW4 waiting for next
zero-current crossing to turn off.
Maximum time is one-half of the
Z
ringing cycle. In this transition
state, current that is limited to the
On
Off
On
Off
break switch dc current limit
value will be sourced from the
ring node of the SLIC.
Zero-cross current has occurred On
Off
Off
Off
2.3.5 Break-Before-Make Operation
Break-before-make operation of the CPC7593 can be
achieved using two different techniques.
The first method uses manipulation of the (IN_RINGING,
IN_TESTin, IN_TESTout) logic inputs as shown in
“Break-Before-Make Operation Logic Table (Ringing to Talk
Transition)” on page 17.
1. At the end of the ringing state apply the all-off
state (1,0,1). This releases the ringing return
switch (SW3) while the ringing switch remains on
waiting for the next zero current event.
2. Hold the all-off state for at least one-half of a
ringing cycle to assure that a zero crossing event
occurs and that the ringing switch (SW4) has
opened.
3. Apply inputs for the next desired state. For the
talk state, the inputs would be (0,0,0).
Break-before-make operation occurs when the ringing
switch opens before the break switches SW1 and
SW2 close.
2.3.6 Break-Before-Make Operation Logic Table (Ringing to Talk Transition)
State IN_RINGING IN_TESTin IN_TESTout Latch
T_SD
Timing
Break
Switches
Ringing
Return
Switch
(SW3)
Ringing
Switch
(SW4)
Test
Switches
Ringing
1
0
0
-
Off
On
On
Off
All-off ^*
1
0
1
Break-
Before-
1
0
1
Make ^*
Hold this state for at least
one-half of ringing cycle. SW4
waiting for zero current to turn
Off
Off
On
Off
0
Z
off.
Zero current has occurred. SW4
has opened
Off
Off
Off
Off
Talk
0
0
0
Break switches close.
On
Off
Off
Off
* For the CPC7593xA/B versions the input pattern (1,1,1) may also be used for the all-off state.
2.3.7 Alternate Break-Before-Make Operation
The second break-before-make method is also
available for use with all versions of the CPC7593. As
shown in “Truth Table for CPC7593xA and CPC7593xB” on
page 14 and “Truth Table for CPC7593xC and CPC7593xD”
on page 14, the bi-directional T_SD interface disables all
of the CPC7593 switches when pulled to a logic low.
Although logically disabled, an active (closed) ringing
switch (SW4) will remain closed until the next current
zero crossing event.
R04
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