Version 4
SHEET 1 1628 964
WIRE 624 80 624 48
WIRE 784 48 624 48
WIRE 784 64 784 48
WIRE 784 112 704 112
FLAG 784 144 0
FLAG 624 160 0
SYMBOL voltage 624 64 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 10
SYMBOL PTC_resistor 768 48 R0
SYMATTR InstName U1
SYMATTR SpiceModel PTC_SH90
TEXT -184 248 Left 0 !.SUBCKT PTC_SH90 1 2 3 RTH={RTH} TAU={TAU}\n* Model of BC PTC 90 degree thermistor for temperature sensing, part# 2322 671 91104, Digikey part# BC1378\n* PTC is modeled by 4 temperature dependent resistors, 2 in series with a parallel combination of 2\n* It takes 4 pairs of constants to define the slope and intercept for these 4 resistors on a log resistance versus linear temperature graph.\n.PARAM A=6.533\n.PARAM B=-.007318\n.PARAM C=-14.422\n.PARAM D=.05435\n.PARAM F=-136.027\n.PARAM G=.3932\n.PARAM H=-42.37\n.PARAM J=.1395\n* TK is the absolute temperature in kelvins of 0 degrees C.\n.PARAM TK=273.15\nRP 1 2 1MEG\nB1 1 2 I=V(1,2)/(exp(A+(TEMP+TK+V(4))*B)+exp(C+(TEMP+TK+V(4))*D)+1/(1/exp(F+(TEMP+TK+V(4))*G)+1/exp(H+(TEMP+TK+V(4))*J)))\n* V(4) rperesents the temperature rise of the element\n* The thermal time constant of the die is modeled as an RC time constant fed by a current source representing the power disipated in the die.\n* RTH represents the thermal resistance die to ambient and CTH represents the thermal capacity of the mass of the die.\nRTH 4 0 {RTH}\nCTH 4 0 {TAU/RTH}\n*BTH 0 4 I=V(1,2)*V(1,2)/(exp(A+(TEMP+TK+V(4))*B)+exp(C+(TEMP+TK+V(4))*D)+1/(1/exp(F+(TEMP+TK+V(4))*G)+1/exp(H+(TEMP+TK+V(4))*J)))\nBTH 0 4 I=abs(V(1,2)*I(B1))\n* V(3), the middle node on the symbol, is the actual element temperature, represented as voltage, where 1 volt is 1degree C.\nBVT 3 0 V=V(4)+TEMP\n.ENDS
TEXT 1136 152 Left 0 !.op
TEXT 1056 80 Left 0 !.temp 0 150 1
TEXT 56 56 Left 0 ;Component BTH changed to \nBTH 0 4 I=abs(V(1,2)*I(B1))\n \nNow it fails if V1 is set to 10V, ok with V1=1V.