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CRxxxx series

Description

The CR range of protectors are based on the proven

technology of the T10 thyristor product. Designed for

transient voltage protection of telecommunications

equipment, it provides higher power handling than a

conventional avalanche diode (TVS) and when compared to

a GDT offers lower voltage clamping levels and infinite surge

life.

Packaged in a transfer molded DO-214AA surface mount

outline designed for high speed pick & place machines used

in today’s surface mount assembly lines.

Electrical Charecteristics

The electrical characteristics of a CRXXXX device is similar

to that of a self gated Triac, but the CR is a two terminal

device with no gate. The gate function is achieved by an

internal current controlled mechanism.

Like the T.T.S. diodes, the CRXXXX has a standoff voltage

(Vrm) which should be equal to or greater than the operating

voltage of the system to be protected. At this voltage (Vrm)

the current consumption of the CRXXXX is negligible and will

not effect the protected system.

When a transient occurs, the voltage across the CRXXXX

will increase until the breakdown voltage (Vbr) is reached. At

this point the device will operate in a similar way to a T.V.S.

device and is in an avalanche mode.

The voltage of the transient will now be limited and will only

increase by a few volts as the device diverts more current.

As this transient current rises, a level of current through the

device is reached (Ibo) which causes the device to switch to

a fully conductive state such that the voltage across the

device is now only a few volts (Vt). The voltage at which the

device switches from the avalanche mode to the fully

conductive state (Vt) is known as the Breakover Voltage

(Vbo). When the device is in the Vt state, high currents can

be deverted without damage to the CRXXXX due to the low

voltage across the device, since the limiting factor in such

devices is dissipated power (V x I).

Resetting of the device to the non conducting state is

controlled by the current flowing through the device. When

the current falls below a certain value, known as the Holding

Current (Ih), the device resets automatically.

As with the avalanche T.V.S. device, if the CRXXXX is

subjected to a surge current which is beyond its maximum

rating, then the device will fail in short circuit mode, this

ensures that the equipment is ultimately protected.

Selecting A CRXXXX

1. When selecting a CRXXXX device, it is important that the

Vrm of the device is equal to or greater than the operating

voltage of the system.

2. The minimum Holding Current (Ih) must be greater than

the current the system is capable of delivering otherwise the

device will remain conducting following a transient condition.

MIN

I

VT

H

V-I Graph

Illustrating Symbols

and Terms for

the CR Surge

Protection Device.

The CRXXXX Range Can Be Used to Protect Against Surges As Defined In The Following International Standards.

SA

SB

SC

FCC Rules Part 68/D

Metallic

10/560µs

50A

100A

100A

Longitudinal

10/160µs

100A

150A

200A

Bellcore Specification

TR-NWT-001089

10/1000µs

37A

75A

100A

2/10µs

-

-

500A

100v/µs

1KV

1KV

1KV

ITU K-17 (Formerly CCITT)

Voltage Wave Form

100/700µs

-

1.5KV

1.5KV

Current Wave Form

5/310µs

-

38A

38A

VDE 0433

Voltage Wave Form

10/700µs

-

2KV

4.0KV

Current Wave Form

5/310µs

-

50A

100A

C-NET 131-24

Voltage Wave From

0.5/700µs

1.0KV

1.0KV

4.0KV

Current Wave Form

0.8/310µs

25A

25A

100A

IEC 1000-4-5

(Discharge through 2

Ω impendance) I

8/20µs

-

100A

250A

Voltage Wave Form

1-2/50µs

-

300V

500V

ITU K-20

Voltage Wave Form

10/700µs

1000V

10000V

4000V

(Formerly CCITT)

Current Wave Form

5/310µs

25A

25A

100A