CPC7695ZCTR datasheet(18/25 Pages) IXYS

18 / 25 page

INTEGRATED CIRCUITS DIVISION

CPC7695

www.ixysic.com

R01

For start up scenarios 2, 3, 5, and 6 the CPC7695 will

power up in the All-Off state and remain there until the

LATCH pin is pulled low. This allows for an indefinite

All-Off state for boards inserted into a powered system

but are not configured for service or boards that need

to wait for other devices to be configured first.

Start up scenario 4 will start up with all switches in the

All-Off state but upon the acceptance of a valid VDD

the LCAS will revert to any one of the legitimate states

listed in the truth tables and there after may randomly

change states based on input pin leakage currents

and loading. Because the LCAS state after power-up

can not be predicted with this start up condition it

should never be utilized.

On designs that do not wish to individually control the

LATCH pins of multi-port cards it is possible to bus

many (or all) of the LATCH pins together to create a

single board level input enable control.

2.6 VBAT Pin

2.6.1 Protection

2.6.2 Battery Voltage Monitor

The CPC7695 also uses the VBAT pin to monitor

battery voltage. If the system battery voltage is lost,

the CPC7695 immediately enters the All-Off state. It

remains in this state until the system battery voltage is

restored. The device also enters the All-Off state if the

battery voltage rises more positive than about –10V

and remains in the All-Off state until the battery

voltage drops below –15 V. This battery monitor

feature draws a small current from the battery (less

than 1

A typical) and will add slightly to the device’s

overall power dissipation.

This monitor function performs properly if the

CPC7695 and SLIC share a common battery supply

origin. Otherwise, if battery is lost to the CPC7695 but

not to the SLIC, the VBAT pin will be internally biased

by the potential applied to the TBAT or RBAT pins via

the internal protection circuitry’s SCR trigger current

path.

2.7 Ringing To Talk State Switch Timing

The CPC7695 provides, when switching from the

Ringing state to theTalk state, the ability to control the

release timing of the ringing switches SW3 and SW4

relative to the state of the break switches SW1 and

SW2 using simple TTL logic-level inputs. The two

available techniques are referred to as

make-before-break and break-before-make operation.

When the switch contacts of SW1 and SW2 are closed

(made) before the ringing switch contacts of SW3 and

SW4 are opened (broken), this is referred to as

make-before-break operation. Break-before-make

operation occurs when the ringing contacts of SW3

and SW4 are opened (broken) before the switch

contacts of SW1 and SW2 are closed (made). With

the CPC7695, make-before-break and

break-before-make operations can easily be

accomplished by applying the proper sequence of

logic-level inputs to the device.

The logic sequences for either mode of operation are

given in “Operation Logic Table (Ringing to Talk Transition):

Make-Before-Break” on page 19, “Operation Logic Table

(Ringing to Talk Transition): Break-Before-Make” on page 19

and “Alternate Operation Logic Table (Ringing to Talk

Transition): Break-Before-Make” on page 20. Logic states

and explanations are shown in “Truth Tables” on

page 15.

2.7.1 Make-Before-Break Operation

To use make-before-break operation, change the logic

inputs from the Ringing state directly to theTalk state.

Application of theTalk 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 CPC7695 internal protection circuitry

thresholds will be diverted away from the SLIC.

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