Datasheet

-0.25
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
V =5V
I
0 0.5 1 1.5 2 2.5 3
I -OutputCurrent- A
O
OutputVoltageChange-%
1.79
1.792
1.794
1.796
1.798
1.8
3 3.5 4 4.5 5 5.5 6
V -InputVoltage-V
I
I =1.5 A
O
V -OutputVoltage-V
O
TPS54318
www.ti.com SLVS975A –SEPTEMBER 2009–REVISED SEPTEMBER 2013
LOAD REGULATION REGULATION
vs vs
LOAD CURRENT INPUT VOLTAGE
Figure 49. Figure 50.
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 = I
O
2
× R
DS(on)
Pd = ƒsw × I
OUT
× 0.7 × 60 × 10
-9
Psw = 2 × V
IN
2
× ƒsw × Io × 0.25 × 10
-9
Pgd = 2 × V
IN
× 3 × 10
-9
× ƒsw
Pq = 350 × 10
-6
× V
IN
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).
ƒsw is the switching frequency (Hz).
So
Ptot = Pcon + Pd + Psw + Pgd + Pq
For given T
A
,
T
J
= T
A
+ Rth × Ptot
For given T
J
max = 150°C
T
A
max = T
J
max – Rth × Ptot
Where:
Ptot is the total device power dissipation (W).
T
A
is the ambient temperature (°C).
T
J
is the junction temperature (°C).
Rth 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).
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