Datasheet

( ) ( )
= - ´
TH TOT
A max J max
T T R P
= + ´
J A TH TOT
T T R P
= ´ ´ ´
TOT COND SW GD Q
P P P P P
-
= ´ ´
6
Q IN
P 116 10 V
9
GD IN SW
P V 3 10 f
-
= ´ ´ ´
( )
2
9
SW IN SW OUT
P V I 0.25 10f
-
= ´ ´ ´ ´
( )
( )
æ ö
= ´ ´
ç ÷
è ø
2
OUT
COND OUT
DS on
IN
V
P I R
V
TPS54140A
www.ti.com SLVSB55B –MAY 2012–REVISED JANUARY 2014
Power Dissipation Estimate
The following formulas show how to estimate the device power dissipation under continuous conduction mode
(CCM) operation. These equations should not be used if the device is working in discontinuous conduction mode
(DCM).
The power dissipation of the device includes conduction loss (Pcon), switching loss (Psw), gate drive loss (Pgd)
and supply current (Pq).
(54)
(55)
(56)
where
• I
OUT
is the output current (A)
• R
DS(on)
is the on-resistance of the high-side MOSFET (Ω)
• V
OUT
is the output voltage (V)
• V
IN
is the input voltage (V)
• ƒ
SW
is the switching frequency (Hz) (57)
(58)
For given T
A
,
(59)
For given T
JMAX
= 150°C
where
• P
TOT
s 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
J(max)
is maximum junction temperature (°C)
• T
A(max)
is maximum ambient temperature (°C). (60)
There are additional power losses in the regulator circuit due to the inductor ac and dc losses, the catch diode
and trace resistance that will impact the overall efficiency of the regulator.
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