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.
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.
2.3.3 Make-Before-Break Operation - All Versions
Make-Before-Break Ringing to Talk Transition Logic Sequence for All Versions
Ringing
Return
Switches Switch
(SW3)
Ringing
Switch
(SW4)
Break
Test
Switches
INRINGING
INTEST
TSD
State
LATCH
Timing
Ringing
1
0
-
Off
On
On
On
Off
Off
On
On
Off
Off
Off
Off
SW4 waiting for next zero-current crossing to
turn off. Maximum time is one-half of the
ringing cycle. In this transition state current
limited by the dc break switch current limit
value will be sourced from the ring node of
the SLIC.
Make-
before-
break
0
0
0
0
0
Z
Talk
Zero-cross current has occurred
2.3.4 Break-Before-Make Operation - CPC7592xA/B
Break-before-make operation of the CPC7592xA/B
can be achieved using two different techniques.
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.
The first method uses manipulation of the IN
RINGING
and IN
logic inputs as shown in
TEST
“Break-Before-Make Ringing to Talk Transition Logic
Sequence CPC7592xA/B” on page 13.
3. Apply inputs for the next desired state. For the
talk state, the inputs would be (0,0).
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
Break-before-make operation occurs when the ringing
switches open before the break switches SW1 and
SW2 close.
Break-Before-Make Ringing to Talk Transition Logic Sequence CPC7592xA/B
Ringing
Return
Ringing
Switch
(SW4)
Break
Test
Switches
INRINGING
INTEST
TSD
State
LATCH
Timing
Switches Switch
(SW3)
Ringing
All-Off
1
1
0
1
-
Off
On
On
On
Off
Off
Hold this state for at least one-half of the
ringing cycle. SW4 waiting for zero current to
turn off.
Off
Off
0
Z
Break-
Before-
Make
Zero current has occurred.
SW4 has opened
1
0
1
0
Off
On
Off
Off
Off
Off
Off
Off
Talk
Break switches close.
R03
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