PTCSL20T121DBX Vishay, PTCSL20T121DBX Datasheet - Page 4

• Manufacturer Part Number: PTCSL20T121DBX
• Description: Thermistors - PTC 120 OHM 50%
• Manufacturer: Vishay
• Type: PTCr
• Series: PTCSLr

Specifications of PTCSL20T121DBX

• Resistance: 120 Ohms
• Termination Style: Radial
• Operating Temperature Range: - 20 C to + 120 C
• Voltage: 30 V
• Lead Free Status / RoHS Status: Lead free / RoHS 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: 08-Jun-09
R1
R2
s
(see Fig. 2), so the comparator's output voltage V
+ θ
Fig. 1 Typical comparator circuit
s
, causing V
R
PTC
thermistor
R
s
p
O
to switch to a high level sufficient to activate an alarm, relay or power shutdown circuit.
As soon as one or more of the windings becomes too hot, the
motor is switched off.
R
f
PTC Thermistors, Mini Radial Leaded
for Over-Temperature Protection
For technical questions, contact:
Fig. 3 Temperature protection of electric motors
+ θ
+ θ
R
L
+ θ
V
O
O
will be low. If an equipment overtemperature occurs, the PTC
V
[e-mail]
O
2381 671 911../PTCSL..T....BE
n
, whereupon its resistance will increase to a value
(R1 = R2)
R
p
< R
Fig. 2 Typical switch characteristic
s
temperature
Trigger
T
Vishay BCcomponents
n
(R1 = R2)
R
p
> R
s
T (°C)
www.vishay.com
p
) is
63