Th yr i s t o r s (S i BOD™ Br e a k o ve r De vi c e s )
S i B OD S e r i e s
Ap p l i c a t i o n N o t e s
The Added Crydom Benefit
When a transient occurs, the voltage across
the SiBOD will increase until the breakdown
voltage (VBR) is reached. At this point the
device will operate in a similar way to a
TVS device and is in an avalanche mode.
Crydom Thyristors (SiBOD™ Breakover
Devices) offer the highest quality and
performance. They also come with an
added benefit – service and technical
assistance to help ensure optimum pro-
tection for your telecommunications
application.
PABX PROTECTION
CR1300SB
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), causing the device to switch to a
fully conductive state such that the volt-
age 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
diverted without damage to the SiBOD
due to the low voltage across the device,
since the limiting factor in such devices is
dissipated power (V X I).
CR1300SB
SiBOD Series
The Crydom SiBOD is a four-layer thyristor-
based protector designed specifically for
telecommunications applications. It has
greater capacity for diverting surge cur-
rents than an avalanche TVS device.
DC SUPPLY
V
C
I
H >
R
R
Equipment
to be
protected
V
C
The Crydom series protector is based on
the proven technology of the SiBOD prod-
uct. Designed for transient voltage protec-
tion of telecommunications equipment, it
provides higher power handling than a
conventional avalanche diode (TVS), and
when compared to a GDT offers lower volt-
age clamping levels and infinite surge life.
SLIC PROTECTION
Line
CR0640SB
To SLIC
CR0640SB
Line
Resetting of the device to the nonconduct-
ing 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.
Electrical Characteristics
or
Line
The electrical characteristics of the
SiBOD devices are similar to those of a
self-gated Triac, but the SiBOD are two-
terminal devices with no gate. The gate
function is achieved by an internal current
controlled mechanism.
(-)
(-)
(-)
(+) To SLIC
CR0640SB
As with the avalanche TVS device, if the
SiBOD device is subjected to a surge
current that is beyond its maximum rating,
the device will fail in short-circuit mode,
which ensures that the equipment is
ultimately protected.
Line
Like the TVS diodes, the SiBOD have a
stand-off voltage (VRM) that 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 SiBOD
are negligible and will not effect the pro-
tected system.
COMPLETE PC BOARD
OPERATION PROTECTION
Integrated
SLIC
On-hook
Line
CR0640
SB
(-)
(-)
(-)
CR2300
SB
Off-hook
Ring
(+)
relay
On-hook
Off-hook
Line
Primary
protection
on-hook
Secondary
protection
off-hook
Ring
Generator
-V
Battery
or
Ring
Detection
Circuit
2
To Order: 1-877-502-5500 Fax: 1-858-715-7280