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R04

CPC7592

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

2.3.5 Break-Before-Make Operation - All Versions

The second break-before-make method for the

CPC7592xA/B is also the only method available for

the CPC7592xC. As shown in “CPC7592xA and

CPC7592xB Truth Table” on page 10 and “CPC7592xC Truth

disables all of the CPC7592 switches when pulled to a

logic low. Although logically disabled, an active

(closed) ringing switch (SW4) will remain closed until

the next zero crossing current event.

As shown in the table “Break-Before-Make Ringing to Talk

Transition Logic Sequence for all Versions” on page 15, this

operation is similar to the one shown in

“Break-Before-Make Operation - All Versions” on page 14,

except in the method used to select the all off state,

reconfigured for the talk state.

1.

This opens the ringing return switch (SW3) and

prevents any other switches from closing.

2.

the ringing cycle period to allow sufficient time for

a zero crossing current event to occur and for the

circuit to enter the break-before-make state.

3.

4.

activate the break switches.

states are “0” which overrides the logic input pins and

forces an all off state and “Z” which allows normal

switch control via the logic input pins. This requires the

use of an open-collector or open-drain type buffer.

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