1littelfuse.com
© 2018 Littelfuse, Inc. Revised: February 26, 2018
Specifications are subject to change without notice.
Power Thermistors
Description
Littelfuse inrush current limiters (power thermistors) are specially
formulated and processed NTC thermistors suitable for
suppressing high inrush currents in switching power supplies and
other applications where the high initial starting currents are
undesirable. Their unique design enables them to handle extremely
high current and voltage levels. In a typical power supply
application, the inrush current limiting power thermistor is used in
series with the filter capacitors. Upon application of the initial
voltage, the device, due to its relatively high resistance, limits the
current flow to an acceptable level until the capacitors are charged.
Thereafter, the device decreases in resistance substantially to a
level where the voltage drop across it is negligible.
Dimensions
A B C D
0.310”
Max
0.700”
Min
See Dim
“D”
See Dim
“T”
Dimensions shown in inches.
ST Series Inrush Current Limiters
“.900" MIN
PROTECTIVE COATING
TINNED SOLDERABLE WIRE
SEE CHART FOR LEAD DIAMETER
“D”
INRUSH CURRENT LIMITING POWER THERMISTORS
0.310" NOM
“T”
.700"
MIN
PROTECTIVE
COATING
TINNED SOLDERABLE WIRE
SEE CHART FOR LEAD DIAMETER
See Dim
“D”
0.310"
NOM
See Dim
“T”
AC
BD
A B C D
Part Numbering System
Note: Not all combinations of Part Number codes are available. Contact Littelfuse for details.
ST 10 0 01 B
No Significance
Multiplier, power of 10
Resistance @ 25ºC
Base Value
Max. Steady State
Current (A)
Series
Inrush Current Limiting Power Thermistor
Power Thermistors
2littelfuse.com
© 2018 Littelfuse, Inc. Revised: February 26, 2018
Specifications are subject to change without notice.
Inrush Current Limiting Power Thermistor
Power Thermistors
Specifications
Part
Number
Resistance
Ohms
@25°C
*Resistance
Tol. ± %
@ 25°C
Imax Max. Steady
State Current IMAX
(A)
Nominal Resistance
@ Max. Current,
RImax (Ohms)
RImax Resis.
@ Max.
Current Ohms
Lead Diameter
Nominal
(Inch)
ST0R713B 0.7 25 13 0.025 0.025 0.04
ST1R005B 130 50.040 0.09 0.024
ST1R020B 115 20 0.030 0.015 0.04
ST1R030B 125 30 0.050 0.015 0.04
ST1R508B 1.5 20 80.040 0.6 0.032
ST2R018B 220 18 0.135 0.03 0.04
ST2R503B 2.5 20 30.070 0.15 0.032
ST2R507B 2.5 20 70.070 0.05 0.032
ST2R509B 2.5 20 90.060 0.04 0.032
ST2R510B 2.5 20 10 0.200 0.04 0.04
ST10001B 10 20 10.090 0.65 0.024
ST10003B 10 20 3 0.015 0.2 0.032
ST10005B 10 20 5 0.015 0.2 0.04
ST10006B 10 20 6 0.600 0.15 0.04
ST10010B 10 20 10 0.030 0.1 0.04
ST12001B 12 20 10.150 1.19 0.032
ST15004C 15 20 40.050 0.25 0.032
ST16002D 16 20 20.040 0.47 0.032
ST20001C 20 20 0.3 0.110 10.024
ST20002B 20 20 1.75 0.400 0.6 0.032
ST25002C 25 20 20.100 0.64 0.032
ST20100B 200 20 0.1 0.170 6.3 0.018
*Resistance tolerances of ± 1%, 2%, and 5% are available upon request
ST Series Inrush Current Limiters
3littelfuse.com
© 2018 Littelfuse, Inc. Revised: February 26, 2018
Specifications are subject to change without notice.
Disclaimer Notice - Information furnished is believed to be accurate and reliable. However, users should independently evaluate the suitability of and test each
product selected for their own applications. Littelfuse products are not designed for, and may not be used in, all applications. Read complete Disclaimer Notice at:
www.littelfuse.com/disclaimer-electronics
Specifications
Part
Number
Resistance
Ohms
@25°C
*Resistance
Tol. ± %
@ 25°C
Imax Max.
Steady State
Current IMAX (A)
Nominal Resistance
@ Max. Current,
RImax (Ohms)
RImax Resis.
@ Max.
Current Ohms
Temperature
Coefficient
(% / °C) @ 25°C
Lead Diameter
Nominal
(Inch)
Temperature
Rating
(ºC)
ST2R515B 0.7 25 13 0.500 0.025 _0.04 _
ST4R0 05B 130 50.250 0.09 _ 0.024 _
ST5R002B 115 20 0.470 0.015 _0.04 _
ST5R004B 125 30 1.000 0.015 _0.04 _
ST5R005B 1.5 20 80.600 0.6 _0.032 _
ST7R004B 220 18 1.075 0.03 _0.04 _
ST8R001B 2.5 20 30.740 0.15 _0.032 _
ST8R003B 2.5 20 71.485 0.05 _0.032 _
ST8R006B 2.5 20 9 _ 0.04 -4.4 0.032 +300 (Max)
ST30002B 10 20 10.280 0.65 _0.024 _
ST30003B 10 20 3 0.135 0.2 _0.032 _
ST33001B 10 20 5 0.650 0.2 _0.04 _
ST33001C 10 20 6 0.200 0.15 _0.04 _
ST33001D 10 20 10 0.200 0.1 _ 0.04 _
ST3R008B 12 20 10.150 1.19 _0.032 _
ST3R017B 15 20 40.100 0.25 _ 0.032 _
ST40002B 16 20 21.19 0 0.47 _ 0.032 _
ST5R006B 20 20 0.3 6.300 1 _ 0.024 _
ST5R007B 20 20 1.75 0.640 0.6 _ 0.032 _
ST5R014B 25 20 20.460 0.64 _0.032 _
ST5R008B 200 20 0.1 0.700 6.3 _0.018 _
* Resistance tolerances of ± 1%, 2%, and 5% are available upon request
ST Series Inrush Current Limiters
Power Thermistors
Inrush Current Limiting Power Thermistor
Power Thermistors
