PTCSL40T121DBE Vishay, PTCSL40T121DBE Datasheet - Page 4

• Manufacturer Part Number: PTCSL40T121DBE
• Description: PTC SS LDD 40MM 120C 030 110 B E3
• Manufacturer: Vishay

Specifications of PTCSL40T121DBE

• Lead Free Status / RoHS Status: Compliant

APPLICATION SPECIFIC DATA
Negative Temperature Coefficient (NTC) thermistors are well known for temperature sensing. What is not well known, however,
is that Positive Temperature Coefficient (PTC) thermistors can be used for thermal protection. Although their operating principles
are similar, the applications are very different; whereas NTC thermistors sense and measure temperature over a defined range,
PTC thermistors switch at one particular temperature.
Just like thermostats they protect such equipment and components as motors, transformers, power transistors and thyristors
against overtemperature. A PTC thermistor is less expensive than a thermostat, and its switch temperature can be more
accurately specified. It is also smaller and easier to design-in to electronic circuitry.
So how does it work? The PTC thermistor is mounted in thermal contact with the equipment to be protected, and connected into
the bridge arm of a comparator circuit, such as shown in Fig. 1. At normal temperature, the PTC thermistor resistance (R
lower than R
thermistor will quickly heat up to its trigger or nominal reference temperature T
much higher than R
APPLICATION EXAMPLES
Document Number: 29012
Revision: 31-Aug-06
As soon as one or more of the windings becomes too hot, the
motor is switched off.
R1
R2
Fig. 3 Temperature protection of electric motors
θ
s
(see Fig. 2), so the comparator's output voltage V
θ
Fig. 1 Typical comparator circuit
θ
s
, causing V
R
PTC
thermistor
R
s
p
θ
O
to switch to a high level sufficient to activate an alarm, relay or power shutdown circuit.
R
f
For technical questions, contact: [e-mail]
MBD129
For Temperature Protection
R
L
PTC Thermistors,
V o
O
will be low. If an equipment overtemperature occurs, the PTC
V o
2381 671 911../PTCSL..T....BE
The PTC thermistors located above the fluid level will be
heated to a temperature greater than T
When immersed they are cooled such that their
resistance value is reduced.
n
, whereupon its resistance will increase to a value
(R1 = R2)
R p
Fig. 2 Typical switch characteristic
R s
Fig. 4 Liquid-level indication
temperature
trigger
T n
Vishay BCcomponents
θ
θ
θ
θ
(R1 = R2)
R p
A
R s
MBD126
n
.
T (°C)
www.vishay.com
p
) is
63