Datasheet

I = 5 A
OUT
48 °C
23 °C
Maximum Temperature = 58 °C
TPS54519
www.ti.com SLVSAT3A –SEPTEMBER 2011–REVISED DECEMBER 2013
Figure 41. Thermal Image
POWER DISSIPATION ESTIMATE
The following formulas show how to estimate the IC power dissipation under continuous conduction mode (CCM)
operation. The power dissipation of the IC (Ptot) includes conduction loss (Pcon), dead time loss (Pd), switching
loss (Psw), gate drive loss (Pgd) and supply current loss (Pq).
Pcon = Io
2
× Rdson_temp
Pd = ƒsw × Iout × 0.7 × 40 × 10
-9
Psw = 0.5 × Vin × Io × ƒsw × 7 × 10
-9
Pgd = 2 × Vin × 6 × 10
-9
× ƒsw
Pq = 455 × 10
-6
× Vin
Where:
IOUT is the output current (A).
Rdson is the on-resistance of the high-side MOSFET (Ω).
VOUT is the output voltage (V).
VIN is the input voltage (V).
ƒsw is the switching frequency (Hz).
So
Ptot = Pcon + Pd + Psw + Pgd + Pq
For given TA,
TJ = TA + Rth × Ptot
For given TJMAX = 140°C
TAmax = TJ max – Rth × Ptot
Where:
Ptot is the total device power dissipation (W).
TA is the ambient temperature (°C).
TJ is the junction temperature (°C).
Rth is the thermal resistance of the package (°C/W).
TJMAX is maximum junction temperature (°C).
TAMAX is maximum ambient temperature (°C).
There are additional power losses in the regulator circuit due to the inductor AC and DC losses and trace
resistance that impact the overall efficiency of the regulator.
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