CPC7595 Datasheet, PDF (17/25 Pages) Clare, Inc. – Line Card Access Switch

CPC7595
2.3.4 Make-Before-Break 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
SW4 waiting for next
zero-current crossing to turn
off. Maximum time is one-half
Make-
of the ringing cycle. In this
Before- 0
0
Break
0
0
Z
transition state, current that is
limited to the break switch dc
On
Off
On
Off
y _{current limit value will be}
r ^{sourced from the ring node of}
the SLIC.
a _Talk
0
0
0
Zero-cross current has
occurred
On
Off
Off
Off
in ^{2.3.5 Break-Before-Make Operation}
Break-before-make operation of the CPC7595 can be
achieved using two different techniques.
The first method uses manipulation of the (IN_RINGING,
lim ^{INTESTin, INTESTout) logic inputs as shown in}
“Break-Before-Make Operation Logic Table (Ringing to Talk
Transition)” on page 17.
e 1. At the end of the ringing state apply the all-off
state (1,0,1). This releases the ringing return
r _{switch (SW3) while the ringing switch remains on}
P ^{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
Hold this state for at least
All-off ^*
1
0
1
one-half of ringing cycle.
SW4 waiting for zero current
Off
Off
On
Off
0
Z
to turn off.
Break-
Before- ₁
0
1
Make ^*
Zero current has occurred.
SW4 has opened
Off
Off
Off
Off
Talk
0
0
0
Break switches close.
On
Off
Off
Off
* For the CPC7595xA/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 CPC7595. As
shown in “Truth Table for CPC7595xA and CPC7595xB” on
page 14 and “Truth Table for CPC7595xC” on page 14, the
bidirectional T_SD interface disables all of the CPC7595
switches when pulled to a logic low. Although logically
R00B
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