TPS61162D_16 Datasheet, PDF (18/29 Pages) Texas Instruments – Dual-Channel WLED Drivers for Smart Phones

TPS61162D
SLVSC13A – JULY 2013 – REVISED MARCH 2016
www.ti.com
Boost converter efficiency is dependent on the resistance of its current path, the switching losses associated with
the switch MOSFET and power diode, and core loss of the inductor. The TPS61162D has optimized the internal
switch resistance, however, the overall efficiency is affected a lot by the DCR of the inductor, equivalent series
resistance (ESR) at the switching frequency, and the core loss. Core loss is related to the core material, and
different inductors have different core loss. For a certain inductor, larger current ripple generates higher
DCR/ESR conduction losses as well as higher core loss. Inductor data sheets do not typically provide the ESR
and core loss information; if needed, consult the inductor vendor for detailed information. Generally, TI
recommends an inductor with lower DCR/ESR for the TPS61162D application. However, there is a trade-off
between the inductance of the inductor, DCR/ESR resistance, and the inductor footprint; furthermore, shielded
inductors typically have higher DCR than unshielded ones. Table 3 lists some recommended inductors for the
TPS61162D. Verify whether the recommended inductor can support the target application using Equation 4,
Equation 5, and Equation 6 as well as bench validation.
PART NUMBER
LPS4018-472ML
LPS4018-682ML
LPS4018-103ML
PCMB051B-4R7M
PCMB051B-6R8M
L (µH)
4.7
6.8
10
4.7
6.8
Table 3. Recommended Inductors
DCR MAX (mΩ)
125
150
200
163
250
SATURATION CURRENT (A)
1.9
1.3
1.3
2.7
2.3
SIZE (L × W × H mm)
4 × 4 × 1.8
4 × 4 × 1.8
4 × 4 × 1.8
5.4 × 5.2 × 1.2
5.4 × 5.2 × 1.2
VENDOR
Coilcraft
Coilcraft
Coilcraft
Cyntec
Cyntec
9.2.2.2 Schottky Diode Selection
The TPS61162D demands a low forward voltage, high-speed, and low-capacitance Schottky diode for optimum
efficiency. Ensure that the diode average and peak current rating exceeds the average output current and peak
inductor current. In addition, the reverse breakdown voltage of the diode must exceed the open LED-protection
voltage. TI recommends ONSemi MBR0540 and NSR05F40 and Vishay MSS1P4 for the TPS61162D.
9.2.2.3 Compensation Capacitor Selection
The compensation capacitor C4 (refer to Additional Application Circuits) connected from the COMP pin to GND,
is used to stabilize the feedback loop of the TPS61162D. A 330-nF ceramic capacitor for C4 is suitable for most
applications. A 470-nF is also acceptable for some applications, and customers are suggested to verify it in their
applications.
9.2.2.4 Output Capacitor Selection
Selection of the output capacitor is primarily to meet the requirement for the output ripple and loop stability. The
output ripple voltage is related to the capacitance and the ESR of the capacitor. A 1-µF to 2.2-µF ceramic type
X5R or X7R capacitor is recommended. Ceramic capacitors have low ESR so the contribution of the ESR
component to the output ripple is negligible. Assuming a capacitor with zero ESR, the output ripple can be
calculated with Equation 7.
V_ripple
=
(V_OUT
V_OUT
- V_IN ) ´ I_OUT
´ F_S ´ C_OUT
where
• V_ripple = peak-to-peak output ripple
(7)
The additional part of ripple caused by the ESR is calculated using V_{ripple_ESR} = I_OUT × R_ESR and can be ignored
for ceramic capacitors.
NOTE
Capacitor degradation greatly increases the ripple. Select a capacitor with 50-V rated
voltage to reduce the degradation at the output voltage. If the output ripple is too large,
choosing a capacitor with less of a degradation effect or with a higher-rated voltage could
be helpful.
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