CPC7695

R01

www.ixysic.com

19

Operation Logic Table (Ringing to Talk Transition): Make-Before-Break

2.7.2 Break-Before-Make Operation

Break-before-make operation of the CPC7695 can be

achieved using two different techniques.

“Operation Logic Table (Ringing to Talk Transition):

Break-Before-Make” on page 19.

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 (SW4)

remains active 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 has opened.

3.

Apply inputs for the next desired state. For

theTalk 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.

Operation Logic Table (Ringing to Talk Transition): Break-Before-Make

State

Latch

Timing

Break

Switches

Ringing

Return

Switch

(SW3)

Ringing

Switch

(SW4)

Test

Switches

Ringing

1

0

0

0Z

-Off

On

On

Off

Make-

Before-

Break

00

0

SW4 waiting for next

zero-current crossing to turn

off. Maximum time is one-half

of the ringing cycle. In this

transition state, current that is

limited to the break switch

DC current limit value will be

sourced from the ring node of

the SLIC.

On

Off

On

Off

Talk

0

0

0

Zero-cross current has

occurred

On

Off

Off

Off

State

Timing

Break

Switches

Ringing

Return

Switch

(SW3)

Ringing

Switch

(SW4)

Test

Switches

Ringing

1

0

0

0Z

-Off

On

On

Off

10

1

Hold this state for at least

one-half of ringing cycle. SW4

waiting for zero current to turn off.

Off

Off

On

Off

Break-

Before-

10

1

Zero current has occurred. SW4

has opened

Off

Off

Off

Off

Talk

0

0

0

Break switches close.

On

Off

Off

Off

* For the CPC7695xA/B versions the input pattern (1,1,1) may also be used for the All-Off state.