Datasheet

I
swpeak
+
Vin D
2 ƒs L
)
I
out
1 * D
I
avg
+
(
1 * D
)
lsw +
Vin
Vout
2.8 A with lsw + minimum switch current of the TPS65161 (2.8 A).
D + 1 *
Vin h
Vout
TPS65161
TPS65161A, TPS65161B
SLVS617E –APRIL 2006–REVISED MARCH 2013 www.ti.com
Table 1. Input Capacitor Selection
CAPACITOR VOLTAGE RATING COMPONENT SUPPLIER COMMENTS
22 μF/1210 16 V Taiyo Yuden EMK325BY226MM C
IN
(VINB)
1 μF/1206 16 V Taiyo Yuden EMK316BJ106KL C
IN
(AVIN)
Boost Converter Design Procedure
The first step in the design procedure is to verify whether the maximum possible output current of the boost
converter supports the specific application requirements. A simple approach is to use the converter efficiency, by
taking the efficiency numbers from the provided efficiency curves or to use a worst-case assumption for the
expected efficiency, e.g., 80%.
1. Duty Cycle:
2. Maximum output current:
3. Peak switch current:
With
Isw = converter switch current (minimum switch current limit = 2.8 A)
fs = converter switching frequency (typical 500 kHz/750 kHz)
L = Selected inductor value
η = Estimated converter efficiency (use the number from the efficiency curves or 0.8 as an estimation)
The peak switch current is the steady-state peak switch current that the integrated switch, inductor, and external
Schottky diode must be able to handle. The calculation must be done for the minimum input voltage where the
peak switch current is highest.
Inductor Selection (Boost Converter)
The TPS65161 operates typically with a 10-μH inductor. Other possible inductor values are 6.8-μH or 22-μH. The
main parameter for the inductor selection is the saturation current of the inductor, which should be higher than
the peak switch current as previously calculated, with additional margin to cover for heavy load transients. The
alternative, more conservative approach, is to choose the inductor with saturation current at least as high as the
typical switch current limit of 3.5 A. The second important parameter is the inductor dc resistance. Usually, the
lower the dc resistance the higher the efficiency. The efficiency difference between different inductors can vary
between 2% to 10%. Possible inductors are shown in Table 2.
Table 2. Inductor Selection (Boost Converter)
INDUCTOR VALUE COMPONENT SUPPLIER DIMENSIONS in mm Isat/DCR
22 μH Coilcraft MSS1038-103NX 10,2 × 10,2 × 3,6 2.9 A/73 mΩ
22 μH Coilcraft DO3316-103 12,85 × 9,4 × 5,21 3.8 A/38 mΩ
10 μH Sumida CDRH8D43-100 8,3 × 8,3 × 4,5 4.0 A/29 mΩ
10 μH Sumida CDH74-100 7,3 × 8,0 × 5,2 2.75 A/43 mΩ
10 μH Coilcraft MSS1038-103NX 10,2 × 10,2 × 3,6 4.4 A/35 mΩ
6.8 μH Wuerth Elektronik 7447789006 7,3 × 7,3 × 3,2 2.5 A/44 mΩ
Output Capacitor Selection (Boost Converter)
For best output voltage filtering, a low ESR output capacitor is recommended. Ceramic capacitors have a low
ESR value and work best with the TPS65161. Usually, three 22-μF ceramic output capacitors in parallel are
sufficient for most applications. If a lower voltage drop during load transients is required, more output
capacitance can be added. See Table 3 for the selection of the output capacitor.
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