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pbonesteak
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Homework Statement
Q4) Calculate the thermal resistance of the heat sink required for the regulator of Q3 above given the information below [from the datasheet] and the data in the table.
Q3 FIGURE 2 shows an adjustable voltage regulator using the LT1083*. The LT1083 develops a 1.25V reference voltage between the output and the adjust terminal. By placing a resistor R1 between these two terminals, a constant current is caused to flow through R1 and down through R2 to set the overall output voltage. If VIN = 18 V, determine the range over which the output voltage can be varied.
Homework Equations
My formula
PD=Vin-Vout*Iout
θ Jct = T(jmax) - TA / PD
The Attempt at a Solution
PDmax = 18V+10% - 15V*1A = 4.8W
Control Section θ Jct = 125-75/4.8 = 10.4 °C/W
Power section θ Jct = 150-75/4.8 = 15.6 °C/W
The data sheet given is here
https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiGuOeymZ3KAhUC_SwKHR6TCCAQFggdMAA&url=http://www.linear.com/docs/3741&usg=AFQjCNE8-DSdhVtLg7527HpB0xFgb3dF6g
This is as far as I get. Theres so much info on the LT1083 datasheet I just need steering in a direction.
Any suggesgions much appreciated
Regards