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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.
V
BR
MIN
V
RM
V
BO
I
RM
I
BO
I
VT
H
I
T
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 2Ω 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
