NTC THERMISTORS: TYPE CL NTC DISCS FOR INRUSH CURRENT LIMITING g DESCRIPTION: Disc thermistor with uninsulated lead-wires. FEATURES: Low cost solid state device for inrush current suppression Excellent mechanical strength Wide operating temperature range: -50C to 175C Suitable for PCB mounting Available as a standard with kinked leads and on tape and reel to EIA RS-468A for automatic insertion Max* Equation constants for Approx. Res. Under Load at % C (max)** x Steady resistance under load *** Max. Rated Current m Farads Res State Disc Disc Lead Lead Current Diss. Time 25C Current Dia. Thick. Spacing Dia. 120 240 Range Const. Const. TYPE 25% AMPS (Max) (Max) (Ref.) AWG VAC VAC X Y Min.I / Max.I 25% 50% 75% 100% (mW/C) (sec.) Fig. 1 (ohms) (RMS) (in.) (in.) (in.) 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 25 100 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 60 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 25 100 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 25 100 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 25 120 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 25 100 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 25 100 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 25 100 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 30 120 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 30 120 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 30 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 90 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 30 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 90 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 15 110 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 9 130 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 15 110 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 9 130 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 15 110 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 9 130 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 30 OPTIONS: DATA: For kinked leads, add suffix A *maximum rating at 25C or For tape and reel, add suffix B I = (1.14250.0057 x T ) x I 25C derated A max For tape and reel, add suffix AB for ambient temperatures other than 25C. Other tolerances in the range 0.7 to 120 **maximum ratings Other tolerances, tolerances at other temperatures Y ***R =X1 where X and Y are found in the table above 0 Alternative lead lengths, lead materials, insulations NTC THERMISTORS: TYPE CL g NTC DISCS FOR INRUSH CURRENT LIMITING R I -t TYPICAL POWER SUPPLY CIRCUIT INRUSH CURRENT LIMITERS IN Maximum permissible surge current at turn-on SWITCHING POWER SUPPLIES Matching the thermistor to the size of the filter capacitors The problem of current surges in switch-mode power supplies Maximum value of steady state current is caused by the large filter capacitors used to smooth the rip- Maximum ambient temperature ple in the rectified 60Hz current prior to being chopped at a high frequency. The diagram above illustrates a circuit com- Expected life of the power supply monly used in switching power supplies. Maximum Surge Current The main purpose of limiting inrush current is to prevent In the circuit above the maximum current at turn-on is the components in series with the input to the DC/DC convertor peak line voltage divided by the value of R for 120v, it is 2 from being damaged. Typically, inrush protection prevents = approximately 120 x /R . Ideally, during turn-on R should be I I nuisance blowing of fuses or breakers as well as welding of very large, and after the supply is operating, should be switch contacts. Since most thermistor materials are very reduced to zero. The NTC thermistor is ideally suited for this nearly ohmic at any given temperature, the minimum no-load application. It limits surge current by functioning as a power resistance of the thermistor is calculated by dividing the peak resistor which drops from a high cold resistance to a low hot input voltage by the maximum permissible surge current in resistance when heated by the current flowing through it. the power supply (V ). / peak Imax surge Some of the factors to consider when designing NTC ther- mistor as an inrush current limiter are: