CPC7592

R04

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13

Sequence CPC7592xA/B” on page 14, and

“Break-Before-Make Ringing to Talk Transition Logic

Sequence for all Versions” on page 15. 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.

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

2.3.4 Break-Before-Make Operation - CPC7592xA/B

Break-before-make operation of the CPC7592xA/B

can be achieved using two different techniques.

“Break-Before-Make Ringing to Talk Transition Logic

Sequence CPC7592xA/B” on page 14.

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).

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