Datasheet

L +
ǒ
V
IN
* V
O
Ǔ
V
O
V
IN
DI f
SW
(Henries)
2 4 6 8 1210
V
IN
– Input Voltage – V
2
1
5
4
6
3
V
BP5
– BP5 Voltage – V
110°C
– 55°C
25°C
2 4 6 8 1210
V
IN
– Input Voltage – V
2
0
8
6
10
4
V
BP10
– BP10 Voltage – V
110°C
– 55°C
25°C
1
7
5
9
3
TPS40054
TPS40055
TPS40057
www.ti.com SLUS593H –DECEMBER 2003–REVISED JULY 2012
BP5 AND BP10 INTERNAL VOLTAGE REGULATORS
Start-up characteristics of the BP5 and BP10 regulators over different temperature ranges are shown in Figure 7
and Figure 8. Slight variations in the BP5 occurs dependent upon the switching frequency. Variation in the BP10
regulation characteristics is also based on the load presented by switching the external MOSFETs.
INPUT VOLTAGE INPUT VOLTAGE
vs vs
BP5 VOLTAGE BP10 VOLTAGE
Figure 7. Figure 8.
SELECTING THE INDUCTOR VALUE
The inductor value determines the magnitude of ripple current in the output capacitors as well as the load current
at which the converter enters discontinuous mode. Too large an inductance results in lower ripple current but is
physically larger for the same load current. Too small an inductance results in larger ripple currents and a greater
number of (or more expensive output capacitors for) the same output ripple voltage requirement. A good
compromise is to select the inductance value such that the converter doesn't enter discontinuous mode until the
load approximated somewhere between 10% and 30% of the rated output. The inductance value is described in
Equation 5.
where
• V
O
is the output voltage
• ΔI is the peak-to-peak inductor current (5)
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