U.S. Sensor
1832 W. Collins Ave
Orange, CA 92867
Tel: 800-777-6467
Tel: 714-639-1000
Fax: 714-639-1220
Email: sales@ussensor.com
Inrush Current Limiting P ower Thermistors
U.S. Sensor’s inrush curren t limiting po wer t h ermistors are specially form ulated and
processed NTC thermistors suitable for suppressing high inrush currents in switching
po wer supplies and other applications where the high initial star ting currents are
und esirable. Their unique design enables them to handle extremely high c urrent and
voltage le vels. In a t ypical power supply a pplicat ion, the device is used in series with th e
filter capacitors. Up on app lication of the in itial voltage, the d evice, 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 a cro ss it is negligible.
Maximum Steady State Current (I max)
For power thermistors, the
maximum continuous steady
state current, either DC or RMS
AC, which the device is capable
of passing. The maximum
steady state current for U.S.
Sensor power thermistors is
determ ined assuming a
maximum operating ambient
temperature of 65°C. If a
specific application requires
ambient temperature operation
above 65°C, custom designed
devices are available.
INRUSH CURRENT LIMITING POWER
THERMISTORS
View Phot o
Resistance At Maximum Current (RImax)
For power thermistors, the approximate resistance of the device under maximum steady
state current conditions.
IN-RUSH CURRENT LIMITING POWER
Part Numb er Ro Resistance
@ 25°C
± 20% Ohms
Imax
Max. Steady State
Current (Amps)
RImax Resis.
@ Max.
Curren t Ohms
Dim. "D"
(Max. Over
Coating)
Dim. "T"
(Max. Over
Coating)
Lead (Dia.
Nom.)
ST1R 020B 1. 0 20 0. 015 1.200 0. 300 0.040
ST1R 030B 1. 0 30 0. 015 1.475 0. 350 0.040
ST2R 018B 2. 0 18 0. 030 1.200 0. 350 0.040
ST2R 503B 2. 5 3 0. 150 0.600 0. 250 0.032
ST2R 507B 2. 5 7 0. 050 0.700 0. 250 0.032
ST2R 509B 2. 5 9 0. 040 0.900 0. 250 0.032
ST2R 510B 2. 5 10 0. 040 1.200 0. 300 0.040
ST2R 515B 2. 5 15 0. 030 1.200 0. 300 0.040
ST5R 002B 5. 0 2 0. 400 0.600 0. 250 0.032
ST5R 005B 5. 0 5 0. 100 0.675 0. 250 0.032
ST5R 007B 5. 0 7 0. 070 0.925 0. 275 0.032
ST7R 004B 7. 0 4 0. 200 0.600 0. 300 0.040
ST10003B 10.0 3 0. 200 0.575 0.300 0.032
ST10005B 10.0 5 0. 200 0.750 0.350 0.040
ST10006B 10.0 6 0. 150 1.175 0.350 0.040
ST10010B 10.0 10 0. 100 1.475 0.300 0.040
ST20002B 20.0 1. 75 0. 600 0.500 0.300 0.032
ST40002B 40.0 2 0. 600 0.725 0.250 0.032
Note: All Dimensions are in Inches
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