CPC7692

R01

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13

Sequence CPC7692BA/B: Break-Before-Make” on

page 13, and “Ringing to Talk Transition Logic

Sequence for all Versions: Break-Before-Make”

on page 14. Logic states and input control settings

are provided in “CPC7692BA and CPC7692BB

Truth Table” on page 10 and “CPC7692BC Truth

Table” on page 10.

2.3.3 Make-Before-Break Operation - All Versions

To use the 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 CPC7692 protection

circuitry thresholds will be diverted away from the

SLIC.

Ringing to Talk Transition Logic Sequence for All Versions: Make-Before-Break

2.3.4 Break-Before-Make Operation - CPC7692BA/B

Break-before-make operation of the CPC7692BA/B

can be achieved using two different techniques.

Transition Logic Sequence CPC7692BA/B:

Break-Before-Make” 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 allowing SW4, the ringing switch, to open.

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.

Ringing to Talk Transition Logic Sequence CPC7692BA/B: Break-Before-Make

State

LATCH

Timing

Break

Switches

Ringing

Return

Switch

(SW3)

Ringing

Switch

(SW4)

Test

Switches

Ringing

1

0

0Z

-Off

On

On

Off

Make-

Before-

Break

00

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.

On

Off

On

Off

Talk

0

0

Zero-cross current has occurred

On

Off

Off

Off

State

LATCH

Timing

Break

Switches

Ringing

Return

Switch

(SW3)

Ringing

Switch

(SW4)

Test

Switches

Ringing

1

0

0Z

-Off

On

On

Off

All-Off

1

1

Hold this state for at least one-half of the ringing

cycle. SW4 waiting for zero current to turn off.

Off

Off

On

Off

Break-

Before-

Make

11

Zero current has occurred.

SW4 has opened

Off

Off

Off

Off

Talk

0

0

Break switches close.

On

Off

Off

Off