CPC7692

14

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R01

2.3.5 Break-Before-Make Operation - All Versions

The second break-before-make method for the

CPC7692BA/B is also the only method available for

the CPC7692BC. As shown in “CPC7692BA and

CPC7692BB Truth Table” on page 10 and

“CPC7692BC Truth Table” on page 10, the

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 “Ringing to Talk Transition

Logic Sequence for all Versions:

Break-Before-Make” on page 14, this operation is

similar to the one shown in “Ringing to Talk

Transition Logic Sequence CPC7692BA/B:

Break-Before-Make” on page 13, except in the

method used to select the all off state, and in when 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.

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

2.4 Data Latch

The CPC7692 has an integrated transparent data

latch. The latch enable operation is controlled by TTL

logic input levels at the LATCH pin. Data input to the

the output of the data latch are internal nodes used for

state control. When the LATCH enable control pin is at

a logic 0 the data latch is transparent and the input

control signals flow directly through the data latch to

the state control circuitry. A change in input will be

reflected by a change in the switch state.

Whenever the LATCH enable control pin is at logic 1,

the data latch is active and data is locked. Subsequent

will not result in a change to the control logic or affect

the existing switch state.

The switches will remain in the state they were in

when the LATCH changes from logic 0 to logic 1 and

will not respond to changes in input as long as the

the latch function. Since internal thermal shutdown

control and external “All-off” control is not affected by

state control.

State

LATCH

Timing

Break

Switches

Ringing

Return

Switch

(SW3)

Ringing

Switch

(SW4)

Test

Switches

Ringing

1

0

0

Z

-

Off

On

On

Off

All-Off

1

0

X0

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

0

0

SW4 has opened

Off

Off

Off

Off

Talk

0

0

0

Z

Close Break Switches

On

Off

Off

Off