CL-70AB - Thermometrics, Inc. - Datasheet.Directory

CL-11 0.7 12 0.77 0.22 0.328 18 2700 600 0.50 -1.18 4.0≤1≤12 14 .06 .04 .02 25

CL-21 1.3 8 0.55 0.21 0.328 18 800 200 0.60 -1.25 3.0≤1≤8.0 .25 .09 .06 .04 15

CL-30 2.5 8 0.77 0.22 0.328 18 6000 1500 0.81 -1.25 2.5≤1≤8.0 .34 .14 .09 .06 25

CL-40 5 6 0.77 0.22 0.328 18 5200 1300 1.09 -1.27 1.5≤1≤6.0 .65 .27 .16 .11 25

CL-50 7 5 0.77 0.26 0.328 18 5000 1250 1.28 -1.27 1.5≤1≤5.0 .96 .40 .24 .16 25

CL-60 10 5 0.77 0.22 0.328 18 5000 1250 1.45 -1.30 1.2≤1≤5.0 1.09 .44 .26 .18 25

CL-70 16 4 0.77 0.22 0.328 18 5000 1250 1.55 -1.26 1.0≤1≤4.0 1.55 .65 .39 .27 25

CL-80 47 3 0.77 0.22 0.328 18 5000 1250 2.03 -1.29 0.5≤1≤3.0 2.94 1.20 .71 .49 25

CL-90 120 2 0.93 0.22 0.328 18 5000 1250 3.04 -1.36 0.5≤1≤2.0 7.80 3.04 1.75 1.18 30

CL-101 0.5 16 0.93 0.22 0.328 18 4000 1000 0.44 -1.12 4.0≤1≤16 .09 .04 .03 .02 30

CL-110 10 3.2 0.40 0.17 0.250 24 600 150 0.83 -1.29 0.7≤1≤3.2 1.10 .45 .27 .18 8

CL-120 10 1.7 0.40 0.17 0.250 24 600 150 0.61 -1.09 0.4≤1≤1.7 1.55 .73 .46 .34 4

CL-130 50 1.6 0.45 0.17 0.250 24 600 150 1.45 -1.38 0.4≤1≤1.6 5.13 1.97 1.13 .75 8

CL-140 50 1.1 0.45 0.17 0.250 24 600 150 1.01 -1.28 0.2≤1≤1.1 5.27 2.17 1.28 .89 4

CL-150 5 4.7 0.55 0.18 0.328 22 1600 400 0.81 -1.26 1.0≤1≤4.7 .66 .27 .16 .11 15

CL-160 5 2.8 0.55 0.18 0.328 22 1600 400 0.60 -1.05 0.8≤1≤2.8 .87 .42 .27 .20 9

CL-170 16 2.7 0.55 0.18 0.328 22 1600 400 1.18 -1.28 0.5≤1≤2.7 1.95 .80 .48 .33 15

CL-180 16 1.7 0.55 0.18 0.328 22 1600 400 0.92 -1.18 0.4≤1≤1.7 2.52 1.11 .69 .49 9

CL-190 25 2.4 0.55 0.18 0.328 22 800 200 1.33 -1.34 0.5≤1≤2.4 2.63 1.04 .60 .41 15

CL-200 25 1.7 0.55 0.18 0.328 22 800 200 0.95 -1.24 0.4≤1≤1.7 2.74 1.18 .70 .49 9

CL-210 30 1.5 0.40 0.20 0.250 24 600 150 1.02 -1.35 0.3≤1≤1.5 3.83 1.50 .87 .60 8

Max*

Steady

Res @ State

25°C Current

TYPE ±25% AMPS

Fig. 1 (ohms) (RMS)

NTC THERMISTORS: TYPE CL

NTC DISCS FOR INRUSH CURRENT LIMITING

DESCRIPTION:

Disc thermistor with uninsulated lead-wires.

FEATURES:

•Low cost solid state device for inrush current

suppression

•Excellent mechanical strength

•Wide operating temperature range: -50°C to 175°C

•Suitable for PCB mounting

•Available as a standard with kinked leads and on

tape and reel to EIA RS-468A for automatic insertion

OPTIONS:

•For kinked leads, add suffix “A”

•For tape and reel, add suffix “B”

•For tape and reel, add suffix “AB”

•Other tolerances in the range 0.7Ωto 120Ω

•Other tolerances, tolerances at other temperatures

•Alternative lead lengths, lead materials, insulations

DATA:

*maximum rating at 25ºC or

Iderated = √(1.1425–0.0057 x T

A) x Imax @ 25°C

for ambient temperatures other than 25ºC.

**maximum ratings

***R0=X1Y where X and Y are found in the table above

BOWTHORPE THERMOMETRICS THERMOMETRICS, INC. KEYSTONE THERMOMETRICS CORPORATION

Crown Industrial Estate, Priorswood Road 808 US Highway 1 967 Windfall Road

Taunton, Somerset TA2 8QY UK Edison, New Jersey 08817-4695 USA St. Marys, Pennsylvania 15857-3397 USA

Tel +44 (0) 1823 335200 Tel +1 (732) 287 2870 Tel +1 (814) 834 9140

Fax +44 (0) 1823 332637 Fax +1 (732) 287 8847 Fax +1 (814) 781 7969

Time

Const.

(sec.)

100

120

100

120

110

130

110

130

110

130

Diss.

Const.

(mW/°C)

Equation constants for

resistance under load *** Approx. Res. Under Load at %

Max. Rated Current

Cx(max)**

µFarads

Lead

Spacing

(Ref.)

(in.)

Disc

Thick.

(Max)

(in.)

Disc

Dia.

(Max)

(in.)

Lead

Dia.

AWG @120

VAC @240

VAC XY

Current

Range

Min.I/ Max.I25% 50% 75% 100%

INRUSH CURRENT LIMITERS IN

SWITCHING POWER SUPPLIES

The problem of current surges in switch-mode power supplies

is caused by the large filter capacitors used to smooth the rip-

ple in the rectified 60Hz current prior to being chopped at a

high frequency. The diagram above illustrates a circuit com-

monly used in switching power supplies.

In the circuit above the maximum current at turn-on is the

peak line voltage divided by the value of R; for 120v, it is

approximately 120 x

公

2/RI. Ideally, during turn-on RIshould be

very large, and after the supply is operating, should be

reduced to zero. The NTC thermistor is ideally suited for this

application. It limits surge current by functioning as a power

resistor which drops from a high cold resistance to a low hot

resistance when heated by the current flowing through it.

Some of the factors to consider when designing NTC ther-

mistor as an inrush current limiter are:

•Maximum permissible surge current at turn-on

•Matching the thermistor to the size of the filter

capacitors

•Maximum value of steady state current

•Maximum ambient temperature

•Expected life of the power supply

Maximum Surge Current

The main purpose of limiting inrush current is to prevent

components in series with the input to the DC/DC convertor

from being damaged. Typically, inrush protection prevents

nuisance blowing of fuses or breakers as well as welding of

switch contacts. Since most thermistor materials are very

nearly ohmic at any given temperature, the minimum no-load

resistance of the thermistor is calculated by dividing the peak

input voltage by the maximum permissible surge current in

the power supply (Vpeak/Imax surge).

BOWTHORPE THERMOMETRICS THERMOMETRICS, INC. KEYSTONE THERMOMETRICS CORPORATION

Crown Industrial Estate, Priorswood Road 808 US Highway 1 967 Windfall Road

Taunton, Somerset TA2 8QY UK Edison, New Jersey 08817-4695 USA St. Marys, Pennsylvania 15857-3397 USA

Tel +44 (0) 1823 335200 Tel +1 (732) 287 2870 Tel +1 (814) 834 9140

Fax +44 (0) 1823 332637 Fax +1 (732) 287 8847 Fax +1 (814) 781 7969

NTC THERMISTORS: TYPE CL

NTC DISCS FOR INRUSH CURRENT LIMITING

TYPICAL POWER SUPPLY CIRCUIT

-tº

Energy Surge at Turn-On

At the moment the circuit is energized, the filter caps in a

switcher appear like a short circuit which, in a relatively short

period of time, will store an amount of energy equal to

1⁄2CV2. All of the charge that the filter capacitors store must

flow through the thermistor. The net effect of this large cur-

rent surge is to increase the temperature of the thermistor

very rapidly during the period the capacitors are charging. The

amount of energy generated in the thermistor during this

capacitor-charging period is dependent on the voltage wave-

form of the source charging the capacitors. However, a good

approximation for the energy generated by the thermistor dur-

ing this period is 1⁄2CV2(energy stored in the filter capacitor).

The ability of the NTC thermistor to handle this energy surge

is largely a function of the mass of the device. This logic can

be seen in the energy balance equation for a thermistor being

self-heated:

Input Energy = Energy Stored

+ Energy Dissipated

or in differential form:

Pdt= HdT+ δ(T– TA)dt

where:

P= Power generated in the NTC

t= Time

H= Heat capacity of the thermistor

T= Temperature of the thermistor body

δ= Dissipation constant

TA= Ambient temperature

During the short time that the capacitors are charging (usu-

ally less than 0.1 second), very little energy is dissipated.

Most of the input energy is stored as heat in the thermistor

body.

In the table of standard inrush limiters there is listed a rec-

ommended value of maximum capacitance at 120 volts and

240 volts. This rating is not intended to define the absolute

capabilities of the thermistors; instead, it is an experimental-

ly determined value beyond which there may be some reduc-

tion in the life of the inrush current limiter.

Maximum Steady-State Current

The maximum steady-state current rating of a thermistor is

mainly determined by the acceptable life of the final products

for which the thermistor becomes a component. In the

steady-state condition, the energy balance in the differential

equation already given reduces to the following heat balance

formula:

Power = I2R = δ(T – TA)

As more current flows through the device, its steady-state

operating temperature will increase and its resistance will

decrease. The maximum current rating correlates to a

maximum allowable temperature.

In the table of standard inrush current limiters is a list of val-

ues for resistance under load for each unit, as well as a rec-

ommended maximum steady-state current. These ratings

are based upon standard PC board heat sinking, with no air

flow, at an ambient temperature of 25°C. However, most

power supplies have some air flow, which further enhances

the safety margin that is already built into the maximum cur-

rent rating. To derate the maximum steady state current for

operation at elevated ambient temperatures, use the following

equation:

Iderated = √(1.1425–0.0057 x T

A) x Imax @ 25°C

Inrush Current Limiters

BOWTHORPE THERMOMETRICS THERMOMETRICS, INC. KEYSTONE THERMOMETRICS CORPORATION

Crown Industrial Estate, Priorswood Road 808 US Highway 1 967 Windfall Road

Taunton, Somerset TA2 8QY UK Edison, New Jersey 08817-4695 USA St. Marys, Pennsylvania 15857-3397 USA

Tel +44 (0) 1823 335200 Tel +1 (732) 287 2870 Tel +1 (814) 834 9140

Fax +44 (0) 1823 332637 Fax +1 (732) 287 8847 Fax +1 (814) 781 7969