CPC7592 Datasheet, PDF (13/20 Pages) Clare, Inc. – Line Card Access Switch

CPC7592
Transition Logic Sequence for all Versions” on
page 14. Logic states and input control settings are
provided in “CPC7592xA and CPC7592xB Truth
Table” on page 10 and “CPC7592xC Truth Table” on
page 10.
2.3.3 Make-Before-Break Operation - All Versions
To use make-before-break operation, change the logic
inputs from the ringing state directly to the talk state.
Application of the talk state opens the ringing return
switch, SW3, as the break switches SW1 and SW2
close. The ringing switch, SW4, remains closed until
the next zero-crossing of the ringing current. While in
the make-before-break state, ringing potentials in
excess of the CPC7592 protection circuitry thresholds
will be diverted away from the SLIC.
State
Ringing
Make-
before-
break
Talk
IN_RINGING
1
0
0
Make-Before-Break Ringing to Talk Transition Logic Sequence for All Versions
IN_TEST LATCH
0
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
limited by the dc break switch current limit
On
Off
On
Off
value will be sourced from the ring node of
the SLIC.
Zero-cross current has occurred
On
Off
Off
Off
2.3.4 Break-Before-Make Operation - CPC7592xA/B
Break-before-make operation of the CPC7592xA/B
can be achieved using two different techniques.
The first method uses manipulation of the IN_RINGING
and IN_TEST logic inputs as shown in
“Break-Before-Make Ringing to Talk Transition Logic
Sequence CPC7592xA/B” on page 13.
1. At the end of the ringing state apply the all off
state (1,1). This releases the ringing return
switch (SW3) while the ringing switch (SW4)
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 SW4, the ringing switch, has
opened.
3. Apply inputs for the next desired state. For the
talk state, the inputs would be (0,0).
Break-before-make operation occurs when the ringing
switches open before the break switches SW1 and
SW2 close.
State
Ringing
All-Off
Break-
Before-
Make
Talk
IN_RINGING
1
1
1
0
Break-Before-Make Ringing to Talk Transition Logic Sequence CPC7592xA/B
IN_TEST LATCH
0
1
0
1
T_SD
Timing
Break
Switches
Ringing
Return
Switch
(SW3)
Ringing
Switch
(SW4)
Test
Switches
-
Off
On
On
Off
Hold this state for at least one-half of the
ringing cycle. SW4 waiting for zero current to Off
Off
On
Off
turn off.
Z
Zero current has occurred.
SW4 has opened
Off
Off
Off
Off
0
Break switches close.
On
Off
Off
Off
R03
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