arhi
Member
hm .. when the sw engineer goes up too deep into hw some basics constantly pop up.. good thing is there's bunch of you I can bother every time I notice that...
Heat dissipation ... I have no idea what's this all about ... (ok, I know "why" the heat is dissipating) ... in the sense that, if it is getting hot - I put one with higher rating - if it is warm I add big heat sink + fan if needed... being surrounded with computer equipment most part of my life, having different CPU heat sinks w/o fan's a fact.
Now, to ask the darn question ....
P = V * I
so simple formula .. (I saw it in few threads before) ... or:
Ppsu = Pout*(1-EFF)/(EFF) //power supply heat, EFF == efficiency
Pq = Logic Supply Voltage x Logic Supply Current + Load supply Voltage x Load Supply Current // Device power consumption under quiescent, no load, conditions
Pcond = 2 x Irms^2 x Rds(on) // Conductive Power Dissipation
Psw = (Eon + Eoff) x F // Switching Power Dissipation
( **broken link removed** )
....
so, bunch of formula's ... all of them (most at least) get the result in W .. interesting ..
so "element" (ic for example) X is producing 6.5W of heat in realtime working conditions, that's important information. In data sheet I can see that "element" operating temperature is -5C - 80C for e.g.
WHAT NOW?
Ther's Heat Sink Temperature Calculator ... not sure I get it completely but seams to me that Thermal Resistance is "how good the element or better say package will tranfer heat to "case" or to "air" ... the Junction is not clear term for me here (yes, english is kinda 5th language for me, sorry) ... sounds like "point where package and heatsink/air meet" but I'm not sure I'm right. Lower the termal resistance, faster the heat will transfer (in order to reach max entropy / make both objects (in this case package and heatsink/air) have same temperature - cooling the hotter one, heating the colder one) ... the amount of newly generated heat is that 6.5W we calculated but how hot is that, with thermal resistance of 3°C/Watt (TO220) how big the heatsink need to be ?! If I do not put heatsink how hot will the TO220 get how fast?
Heat dissipation ... I have no idea what's this all about ... (ok, I know "why" the heat is dissipating) ... in the sense that, if it is getting hot - I put one with higher rating - if it is warm I add big heat sink + fan if needed... being surrounded with computer equipment most part of my life, having different CPU heat sinks w/o fan's a fact.
Now, to ask the darn question ....
P = V * I
so simple formula .. (I saw it in few threads before) ... or:
Ppsu = Pout*(1-EFF)/(EFF) //power supply heat, EFF == efficiency
Pq = Logic Supply Voltage x Logic Supply Current + Load supply Voltage x Load Supply Current // Device power consumption under quiescent, no load, conditions
Pcond = 2 x Irms^2 x Rds(on) // Conductive Power Dissipation
Psw = (Eon + Eoff) x F // Switching Power Dissipation
( **broken link removed** )
....
so, bunch of formula's ... all of them (most at least) get the result in W .. interesting ..
so "element" (ic for example) X is producing 6.5W of heat in realtime working conditions, that's important information. In data sheet I can see that "element" operating temperature is -5C - 80C for e.g.
WHAT NOW?
Ther's Heat Sink Temperature Calculator ... not sure I get it completely but seams to me that Thermal Resistance is "how good the element or better say package will tranfer heat to "case" or to "air" ... the Junction is not clear term for me here (yes, english is kinda 5th language for me, sorry) ... sounds like "point where package and heatsink/air meet" but I'm not sure I'm right. Lower the termal resistance, faster the heat will transfer (in order to reach max entropy / make both objects (in this case package and heatsink/air) have same temperature - cooling the hotter one, heating the colder one) ... the amount of newly generated heat is that 6.5W we calculated but how hot is that, with thermal resistance of 3°C/Watt (TO220) how big the heatsink need to be ?! If I do not put heatsink how hot will the TO220 get how fast?