TPS61054_15 Datasheet, PDF (15/30 Pages) Texas Instruments – High-Power White LED Driver 2-mHz Synchronous Boost Converter

www.ti.com
TPS61054, TPS61055
SLUS760B – SEPTEMBER 2007 – REVISED SEPTEMBER 2015
To optimize solution size the TPS6105x device has been designed to operate with inductance values between a
minimum of 1.3 μH and maximum of 2.9 μH. In typical high-current white LED applications a 2.2-μH inductance
is recommended.
To select the boost inductor, TI recommends 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:
I_L
[
I_OUT
+
V_OUT
h V_IN
(1)
I _L(PEAK)
+
V_IN
2
f
D
L
)
(1
I_OUT
* D)
h
with
D
+
V_OUT * V_IN
V_OUT
where
• f = switching frequency (2 MHz)
• L = inductance value (2.2 μH)
• η = estimated efficiency (85%)
(2)
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.
MANUFACTURER
TDK
TAIYO YUDEN
FDK
TDK
COILCRAFT
MURATA
TOKO
Table 4. List of Inductors
SERIES
VLF3010AT
NR3010
MIPSA2520
VLF3014AT
LPS3015
LQH3NP
FDSE0312
DIMENSIONS
2.6 mm × 2.8 mm × 1.0 mm maximum height
3.0 mm × 3.0 mm × 1.0 mm maximum height
2.5 mm × 2.0 mm × 1.2 mm maximum height
2.6 mm × 2.8 mm × 1.4 mm maximum height
3.0 mm × 3.0 mm × 1.5 mm maximum height
3.0 mm × 3.0 mm × 1.5 mm maximum height
3.0 mm × 3.0 mm × 1.2 mm maximum height
I_LIM SETTINGS
1000 mA (typical)
1500 mA (typical)
10.2.1.2.2 Capacitor Selection
10.2.1.2.2.1 Input Capacitor
For good input voltage filtering low ESR ceramic capacitors are recommended. A 10-μF input capacitor is
recommended to improve transient behavior of the regulator and EMI behavior of the total power supply circuit.
The input capacitor must be placed as close as possible to the input pin of the converter.
10.2.1.2.2.2 Output Capacitor
The primary parameter necessary to define the output capacitor is the maximum allowed output voltage ripple of
the converter. This ripple is determined by two parameters of the capacitor, the capacitance and the ESR. It is
possible to calculate the minimum capacitance needed for the defined ripple, supposing that the ESR is zero, by
using Equation 3:
C_min
[
I_OUT
f
ǒ_{VOUT * VIN}Ǔ
DV V_OUT
where
• f is the switching frequency
• ΔV is the maximum allowed ripple.
(3)
With a chosen ripple voltage of 10 mV, a minimum capacitance of 10 μF is needed. The total ripple is larger due
to the ESR of the output capacitor. This additional component of the ripple can be calculated using Equation 4:
Copyright © 2007–2015, Texas Instruments Incorporated
Product Folder Links: TPS61054 TPS61055
Submit Documentation Feedback
15