Datasheet
www.ti.com
APPLICATION INFORMATION
INDUCTOR SELECTON
I
L
[ I
OUT
+
V
OUT
h V
IN
(1)
I
L(PEAK)
+
V
IN
D
2 f L
)
I
OUT
(1 * D) h
with D +
V
OUT
* V
IN
V
OUT
(2)
TPS61050
TPS61052
SLUS525 – MARCH 2007
A boost converter requires two main passive components for storing energy during the conversion. A boost
inductor and a storage capacitor at the output are required. The TPS6105x device integrates a current limit
protection circuitry. The peak current of the NMOS switch is sensed to limit the maximum current flowing through
the switch and the inductor. The typical peak current limit (1000 mA / 1500 mA / 2000 mA) is user selectable via
the I
2
C interface.
In order to optimize solution size the TPS6105x device has been designed to operate with inductance values
between a minimum of 1.3 µ H and maximum of 2.9 µ H. In typical high-current white LED applications a 2.2 µ H
inductance is recommended.
To select the boost inductor, it is recommended to keep the possible peak inductor current below the current
limit threshold of the power switch in the chosen configuration. The highest peak current through the inductor
and the power switch depends on the output load, the input and output voltages. Estimation of the maximum
average inductor current and the maximum inductor peak current can be done using Equation 1 and Equation 2 :
with:
f = switching frequency (2 MHz)
L = inductance value (2.2 µ H)
η = estimated efficiency (85%)
For example, for an output current of 500 mA at 5 V, the TPS6105x device needs to be set for a 1000 mA
current limit operation together with an inductor supporting this peak current.
The losses in the inductor caused by magnetic hysteresis losses and copper losses are a major parameter for
total circuit efficiency.
Table 3. List of Inductors
MANUFACTURER SERIES DIMENSIONS ILIM SETTINGS
TDK VLF3010AT 2,6 mm × 2,8 mm × 1,0 mm max. height
1000 mA (typ.)
TAIYO YUDEN NR3010 3,0 mm × 3,0 mm × 1,0 mm max. height
TDK VLF3014AT 2,6 mm × 2,8 mm × 1,4 mm max. height
COILCRAFT LPS3015 3,0 mm × 3,0 mm × 1,5 mm max. height 1500 mA (typ.)
MURATA LQH3NP 3,0 mm × 3,0 mm × 1,5 mm max. height
TOKO FDSE0312 3,0 mm × 3,0 mm × 1,2 mm max. height 2000 mA (typ.)
30
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