TPS54560_17 Datasheet, PDF (30/46 Pages) Texas Instruments – 4.5 V to 60 V Input, 5 A, Step Down DC-DC Converter with Eco-mode

TPS54560
SLVSBN0B – MARCH 2013 – REVISED AUGUST 2016
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• trise is the SW terminal voltage rise time and can be estimated by trise = V_IN x 0.16 ns/V + 3 ns
• Q_G is the total gate charge of the internal MOSFET
• I_Q is the operating nonswitching supply current
(53)
Therefore,
P_TOT = P_COND + P_SW + P_GD + P_Q = 0.958 W + 0.118 W + 0.014 W + 0.0018 W = 1.092 W
(54)
For given T_A,
T_J = T_A + R_TH ´ P_TOT
(55)
For given T_JMAX = 150°C
T_A(max) = T_J(max) - R_TH ´ P_TOT
where
• Ptot is the total device power dissipation (W)
• T_A is the ambient temperature (°C).
• T_J is the junction temperature (°C).
• R_TH is the thermal resistance of the package (°C/W)
• T_JMAX is maximum junction temperature (°C)
• T_AMAX is maximum ambient temperature (°C).
(56)
There will be additional power losses in the regulator circuit due to the inductor ac and dc losses, the catch diode
and PCB trace resistance impacting the overall efficiency of the regulator.
30
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