Datasheet

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Thermal Calculations
TPS5420-EP
SLVS717 – DECEMBER 2006
ADVANCED INFORMATION (continued)
The following formulas show how to estimate the device power dissipation under continuous conduction mode
operations. They should not be used if the device is working at light loads in the discontinuous conduction mode.
Conduction loss: Pcon = I
OUT
2
× r
DS(on)
× V
OUT
/V
IN
Switching loss: Psw = V
IN
× I
OUT
× 0.01
Quiescent current loss: Pq = V
IN
× 0.01
Total loss: Ptot = Pcon + Psw + Pq
Given T
A
=> Estimated junction temperature: T
J
= T
A
+ Rth × Ptot
Given T
JMAX
= 125 ° C => Estimated maximum ambient temperature: T
AMAX
= T
JMAX
Rth × Ptot
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