Datasheet

Time = 2 ms/div
2 V/div
5 V/div
2 V/div
C3: EN
C2: V
OUT
C3
C2
C1
C1: V
IN
Time = 2 ms/div
2 V/div
5 V/div
2 V/div
C1: V
IN
C3: EN
C2: V
OUT
C2
C3
C1
Time = 100 s/divm
100 mV/div
C3: V ac coupled
OUT
1 A/div
C4: I
OUT
C4
C3
Time = 4 ms/div
20 mV/div
10 V/div
V V offset
OUT
-3.3
V
IN
( ) ( )
= - ´
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 0.31 W 0.123 W 0.022 W 0.0018 W 0.457 W
TPS54340
www.ti.com SLVSBK0B –OCTOBER 2012–REVISED MARCH 2014
I
Q
is the operating nonswitching supply current.
Therefore,
(53)
For given T
A
,
(54)
For given T
JMAX
= 150°C
(55)
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).
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.
9.2.3 Application Curves
Figure 38. Line Transient (8 V to 40 V)
Figure 37. Load Transient
Figure 39. Start-up With VIN Figure 40. Start-up With EN
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