CPC7594 datasheet(14/20 Pages) IXYS

14 / 20 page

INTEGRATED CIRCUITS DIVISION

www.ixysic.com

R04

CPC7594

The logic sequences for either mode of operation are

provided in “Make-Before-Break Ringing to Talk Transition

Logic Sequence” on page 14, “Break-Before-Make Ringing

to Talk Transition Logic Sequence” on page 15, and

“Alternate Break-Before-Make Ringing to Talk Transition

Logic Sequence” on page 15. Logic states and input

control settings are provided in “CPC7594xA and

CPC7594xB Truth Table” on page 11 and “CPC7594xC Truth

Table” on page 11.

2.3.3 Make-Before-Break Operation

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 CPC7594 protection circuitry thresholds

will be diverted away from the SLIC.

Make-Before-Break Ringing to Talk Transition Logic Sequence

2.3.4 Break-Before-Make Operation

Break-before-make operation of the CPC7594 can be

achieved using two different techniques.

The first method uses manipulation of the INRINGING

and INTEST logic inputs as shown in

“Break-Before-Make Ringing to Talk Transition Logic

Sequence” on page 15.

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.

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.

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.

State

INRINGING

INTEST

LATCH

TSD

Timing

Break

Switches

Ringing

Return

Switch

(SW3)

Ringing

Switch

(SW4)

Test

Switches

Ringing

-Off

Off

Make-

before-

break

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.

Off

Talk

Zero-cross current has occurred

Off

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