Thick Film
2512 Surge Resistors
BSR Series
Features
1.2/50 microsecond 250V pulse
10/700 microsecond 250V pulse
Nickel barrer terminations
Double glass passivation
NOT RECOMMENDED FOR NEW DESIGNS
PWC2512 Preferred
All parts are Pb-free and comply with EU Directive 2011/65/EU amended by (EU) 2015/863 (RoHS3)
Applications
Telephone lines are often subject to a variety of voltage disturbances
which fall into two main categories - short duration, high voltage tran-
sients caused by lightning strikes and longer duration, over voltages which
may be caused by direct connection to mains power lines. The advent of
electronic switching has meant that sophisticated methods of protection
against these two fault conditions has to be incorporated to ensure that
potential damage is limited.
The two types of protection are: primary, which attempts to deal with the
bulk of the energy from a fast transient, particularly lightning strikes and
power crosses and secondary, which provides a further level of protection
to prevent damage to sensitive electronic circuits.
The possibility of disturbances in the line is dependent on the environ-
ment of the equipment installation. In the case of a PABX, where the tel-
ephone line, terminal equipment and the line interface are all installed in
the same building, the possibility of induced lightning transients is greatly
reduced and the opportunity for damage induced by direct connection to
mains is low. For these reasons the degree of protection is much less than
for equipment connected outside the building where the risk increases
dramatically.
BI Technologies is involved in secondary protection for
all types of environment. The BSR Series has been specifically designed
for PABX where cost is of paramount importance. For central switches,
the tip and ring resistors are expected to perform identically to maintain
the correct resistance for a balanced line system. Both resistors are there-
fore generally produced on a common substrate, which may be through
hole or surface mount, and perform close to one another under all
foreseeable fault conditions in both common and differential modes. For
PABX, tracking is not required because an individual resistor is used which
normally runs at low power yet has the ability to withstand considerable
power for long periods and has good characteristics under high voltage
transient conditions.
The BSR Series is a surface mount chip resistor in a standard 2512 pack-
age which utilizes special resistor film to handle the high voltage with
sophisticated laser trimming to prevent flash over. In the event of a very
high voltage pulse the resistor will go open-circuit preventing damage
to surrounding components or the printed circuit board. Two units are
required for each incoming line to protect both tip and ring individually
and collectively. The resistor is made from nonflammable material.
Electrical
Surge Capability, Max.
Standard Resistance Range, Ohms
Standard Resistance Tolerances
Operating Temperature Range
Temperature Coefficient of Resistance, Max.
Power Ratings, Watts, at 70°C ( See Note )
Operating Voltage, Max.
Note: For 2 watts limit part temperature to +155°C
S1.2 / 50 μs, 250 V; 10 / 700 μs, 250 V (ΔR ±5%+0.1Ω)
0.05 to 10K Ohms
±5%, ±10%, ±20% Optional : ±1%, ±2%
-55°C to +125°C
±100ppm/°C above 10 Ohms
1 and 2
100 V dc or √PR whichever is less
General Note
TT Electronics reserves the right to make changes in product specification without notice or liability.
All information is subject to TT Electronics’ own data and is considered accurate at time of going to print.
BI Technologies IRC Welwyn
www.ttelectronics.com/resistors
© TT Electronics plc
02.22
Thick Film 2512 Surge Resistors
BSR Series
NOT RECOMMENDED FOR NEW DESIGNS
Environmental
Short Time Overload, Max.
Temperature Cycling
Moisture Resistance
Load Life
Resistance to Solder Heat
2.5 x rated voltage (ΔR ±1%+0.1 Ω)
-55°C to +125°C, 5 cycles (ΔR ±5%+0.1 Ω)
1,000 hours at 40°C, 95% RH (ΔR ±3%+0.1 Ω)
1,000 hours at 70°C + Rated Voltage, Max. (ΔR ±3%+0.1 Ω)
260°C for 10 sec. (ΔR ±5%+0.1 Ω)
Construction
Glass Passivation:
Glass Protective
Coating
Resistor:
Ruthenium Oxiel
Tin Plating
Nickel Barrier
Substrate Alumina
Thick Film Conductor
General Note
TT Electronics reserves the right to make changes in product specification without notice or liability.
All information is subject to TT Electronics’ own data and is considered accurate at time of going to print.
BI Technologies IRC Welwyn
www.ttelectronics.com/resistors
© TT Electronics plc
02.22
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