CPC7514

10

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R06

3. Functional Description

3.1 Introduction

The CPC7514 High Voltage Quad Analog Switch

Array has four independent symmetrical switches

providing 16 unique operating states. These

operational states and the logical behavior of the

device are shown in the tables given in “Truth

Tables” on page 8. Switch organization consists of

two channels each having a pair of switches. Within

each channel there is a single LATCH input and a

single Temperature Shutdown circuit shared by the

switch pair. Other than these two shared circuits the

performance of each switch within a channel is

independent of the other. As there is no shared

circuitry between the channels, the switches of one

channel are completely independent of the other

channel. Switch utilization under normal operating

conditions allows the switches to be used in any

combination. In designs where the switches will be

required to carry high load currents or operate in

higher temperature environments the thermal

specifications should be reviewed.

Solid-state switch construction of the CPC7514 offers

clean, bounce-free switching with simple logic input

control to provide access to high voltage interfaces

without the impulse noise generated by traditional

electromechanical switching techniques. Simple logic

input control eliminates the additional driver circuitry

required by traditional techniques.

switches are configured as matched pairs, SW1/SW2

and SW3/SW4, for improved performance when

differential access is required. Their symmetrical

construction provides an additional degree of design

flexibility allowing either side of the switch to be

connected to the high voltage network.

Integrated into the CPC7514 switches are active

current limiting and thermal shutdown mechanisms to

provide protection for the electronics being connected

to the high voltage network during a fault condition.

High frequency positive and negative transient

currents such as lightning are reduced by the current

limiting circuitry. Protection from prolonged low

frequency power-cross and DC currents, also reduced

by the current limiting circuitry, is supplemented by

thermal shutdown circuits.

To protect against a high voltage fault in excess of the

CPC7514’s maximum voltage rating, use of an

over-voltage protector is required. The protector must

level below the switches maximum breakdown

voltage. To minimize the stress on the solid-state

contacts, use of a foldback or crowbar type protector is

highly recommended. With proper selection of the

protector, telecom applications using the CPC7514

will meet all relevant ITU, LSSGR, TIA/EIA and IEC

protection requirements.

Operating from a single +3.3V supply the CPC7514

has extremely low power consumption.

3.2 Under-Voltage Switch Lock-Out Circuitry

Smart logic in the CPC7514 provides for switch state

control during both power up and power loss

transitions to prevent undesired connections to high

voltage networks. An internal detector evaluates the

under-voltage switch lock-out circuitry with a rising

circuit overrides user switch control by blocking the

external information at the input pins, and conditioning

internal switch commands to the All-Off state. Upon

set to ensure all internal logic is properly biased and

functional before accepting external switch commands

from the inputs to control the switch states. For a

assure proper logic and switch behavior up to the

moment the switches are forced off and external

inputs are suppressed.

3.3 Switch Logic

threshold, the smart logic places the control logic into