Datasheet

I = 5 A/div
OUT
Time = 5 ms/div
V = 1 V/div
OUT
Time = 500 s/divm
V = 500 mV/div
OUT
TPS54478
SLVSAS2 – JUNE 2011 www.ti.com
Figure 51. HICCUP MODE CURRENT LIMIT Figure 52. START UP CHARACTERISTIC
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
× R
DS_on_Temp
Pd = ƒ
sw
× Io × 0.7 × 40 × 10
–9
Psw = 1/2 × V
in
× Io × ƒ
sw
× 7 × 10
–9
Pgd = 2 × V
in
× ƒ
sw
× 6 × 10
–9
Pq = V
in
× 525 × 10
–6
Where:
I
O
is the output current (A).
R
DS_on_Temp
is the on-resistance of the high-side MOSFET with given temperature (Ω).
V
in
is the input voltage (V).
ƒ
sw
is the switching frequency (Hz).
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