TFPT www.vishay.com Vishay RATIO FORMULA RT = R25 x (9.0014 x 10-1 + 3.87235 x 10-3 (°C)-1 x T + 4.86825 x 10-6 (°C)-2 x T2 + 1.37559 x 10-9 (°C)-3 x T3) T(°C) = 28.54 x (RT/R25)3 - 158.5 x (RT/R25)2 + 474.8 x (RT/R25) - 319.85) RATIO TOLERANCE EXAMPLES:RATIO TOLERANCES At 40 °C, ratio = 1.063 ± 0.5 % (0.005) LOW TEMP.HIGH TEMP.TOL. so, ratio = 1.058 to 1.068 -55 °C +150 °C ± 4 % At 125 °C, ratio = 1.460 ± 3 % (0.044) -40 °C +125 °C ± 3 % so, ratio = 1.416 to 1.504 -20 °C +85 °C ± 2 % At intermediate temperatures, the ratios can be gradually 0 °C +55 °C ± 1 % adapted, for example at 105 °C the ratio tolerance will be +12 °C +40 °C ± 0.5 % ± 2.5 %. For total resistance tolerance, the specific R25 tolerance needs to be multiplied with the ratio tolerance, for example a 100R 1 % at 25 °C will have a maximum resistance at 125 °C of 100R x 1.463 x 1.03 x 1.01 = 152.2 Ω. RATIO RT/R25TCR TYPICAL VALUE Axis Title Axis Title 1.7 10000 4800 10000 1.6 4700 1.5 Max. 4600 1.4 4500 1000 4400 1000 1.3 Min. ) /K 4300 ine 1.2 ne ne ine m ne ne p p 4200 Ratio 1.1 ( 1st li 2nd l 2nd li 2nd l R 4100 1st li 2nd li 1.0 100 TC 4000 100 0.9 3900 0.8 3800 0.7 3700 0.6 10 3600 10 -75 -50 -25 0 25 50 75 100 125 150 -75 -50 -25 0 25 50 75 100 125 150 175 Temperature (°C) Temperature (°C) POWER DERATING Axis Title 110 10000 100 90 80 ) 1000 70 (% 60 ne ne ine f P 70 50 r o 1st li 2nd l 2nd li e w 40 100 Po 30 20 10 0 10 -75 -50 -25 0 25 50 75 100 125 150 175 Temperature (°C) Note • Zero (0 %) power is considered as measuring power that will generate a maximum film temperature increase of 1 °C Revision: 25-Feb-2025 4 Document Number: 33017 For technical questions, contact: nlr@vishay.com THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
