307C Overcurrent Thermistors
Vishay Cera-Mite
PTCR Overcurrent Protection
FEATURES:
A NEW DIMENSION
Sizes For Your Application - Hold currents from 5 mA to 1.5 A are available
in sizes from 4 to 22mm.
The Positive Temperature Coefficient
Resistor’s (PTC thermistor) unique property
of dramatically increasing its resistance
above the curie temperature makes it
an excellent candidate for overcurrent
protection applications. Overcurrent
situations in electronic devices occur
due to voltage fluctuations, changes in
load impedance, or problems with system
wiring. PTC thermistors monitor current in
series connected loads, trip in the event
of excess current, and reset after the
overload situation is removed, creating a
new dimension of flexibility for designers.
Better Protection, Maintenance Free - PTCRs reset after an overcurrent
situation. Protection levels may be set lower than possible with fuses, without
worrying about nuisance trips.
Resetting, Non Cycling - Functioning as a manual reset device, PTCR
overcurrent protectors remain latched in the tripped state and automatically
reset only after voltage has been removed. This prevents continuous cycling,
and protects against reclosing into a fault condition.
Simplified Mounting - PTCRs may be mounted directly inside end use
equipment. Unlike fuses, no bulky fuseholder or access for user replacement
is required.
Ceramic Material Selection - Various curie materials are available to tailor
hold and trip current operating points.
Repeatable, No Hysteresis - After resetting, ceramic PTCRs return to the
initial resistance value, providing repeatable, consistent protection levels.
Unlike polymer type PTCRs, Vishay Cera-Mite devices exhibit no resistance
hysteresis application problems.
APPLICATIONS:
• Telecommunication Products
• Electronic Power Supplies
• Automotive Motor Protection
• Industrial Control Systems
Telecom Line Balance - In telecom circuits matched pairs are used to
maintain line balance. Unlike polymer PTCRs, ceramic devices maintain
balance after resetting.
APPLICATION DATA
This relationship is shown in Fig P-2,
which provides hold current (IH) derating
estimates for ambient temperatures in
excess of 25°C. Five curie materials
illustrate the design flexibility offered by
ceramic PTCR’s.
In a typical current limiter application, the PTC device is connected in series
with a load impedance (Fig P-1). When current (I) flows, internal I2R losses
attempt to increase the PTCR’s temperature. To maintain the low resistance
“on” state, stabilization must occur below the switching temperature, where
the heat generated (I2R) is balanced by heat lost due to radiation and
conduction.
Hold current (IH) is the maximum continuous current at which a PTCR can
be maintained in a low resistance “on” state while operating at rated ambient
temperature (typ 25°C). To prevent nuisance tripping, choose the rated hold
current to be greater than the normal current expected.
Fig P-2
PTC Thermistor Overcurrent Protectors
Ambient Temperature Derating of Hold and
Trip Currents
Since heat dissipated by the device is proportional to the ambient temperature,
hold current must be derated for ambients higher than 25°C according to
the following relationship:
140%
70°C Curie Material
80°C Curie Material
120%
90°C Curie Material
105°C Curie Material
120°C Curie Material
100%
80%
60%
40%
20%
0%
Hold Current (IH) = D(TSW - TA)
RPTC
Where:
Fig P-1
D
= Dissipation Constant
(varies based on disc
size, wire type, &
Typical PTC Current Limiter Application
PTC
coating material)
-10
0
10 20 30 40 50 60 70 80 90 100 110 120
Ambient Temperature (°C)
AC
or
DC
TSW = Switching (Curie)
Temperature of
V
LOAD
PTCR Material
TA = Ambient Temperature
R
PTC= Resistance of PTCR
at 25°C
Document Number: 23089
Revision 14-May-02
www.vishay.com
11
ceramite.support@vishay.com
5秒后页面跳转
AO3401场效应管参数、引脚图、应用原理图
BT131可控硅参数及引脚图、工作原理详解
74LS32芯片参数、引脚图及功能真值表
全球首块英伟达H200交付 黄仁勋“送货上门”
微信公众号
抖音公众号
浙公网安备 33010502006866号 浙ICP备10014259号-119
营业执照ICP证
数据手册
如果您发现信息不准确，
