Fs

V

ripple

V

R

ESR

TPS61165

www.ti.com

SLVS790A – NOVEMBER 2007 – REVISED MAY 2010

TPS61165 has built-in slope compensation to avoid sub-harmonic oscillation associated with current mode

control. If the inductor value is lower than 10mH, the slope compensation may not be adequate, and the loop can

be unstable. Therefore, customers need to verify the inductor in their application if it is different from the

recommended values.

Table 3. Recommended Inductors for TPS61165

L

DCR MAX

SATURATION CURRENT

SIZE

PART NUMBER

VENDOR

(mH)

(m

Ω)

(A)

(L × W × H mm)

A915_Y-100M

10

90

1.3

5.2×5.2×3.0

TOKO

VLCF5020T-100M1R1-1

10

237

1.1

5×5×2.0

TDK

CDRH4D22/HP

10

144

1.2

5×5×2.4

Sumida

LQH43PN100MR0

10

247

0.84

4.5×3.2×2.0

Murata

SCHOTTKY DIODE SELECTION

The high switching frequency of the TPS61165 demands a high-speed rectification for optimum efficiency.

Ensure that the diode’s average and peak current rating exceeds the average output current and peak inductor

current. In addition, the diode’s reverse breakdown voltage must exceed the open LED protection voltage. The

ONSemi MBR0540 and the ZETEX ZHCS400 are recommended for TPS61165.

COMPENSATION CAPACITOR SELECTION

The compensation capacitor C3 (see the block diagram), connected from COMP pin to GND, is used to stabilize

the feedback loop of the TPS61165. Use 220nF ceramic capacitor for C3.

INPUT AND OUTPUT CAPACITOR SELECTION

The output capacitor is mainly selected to meet the requirements for the output ripple and loop stability. This

ripple voltage is related to the capacitor’s capacitance and its equivalent series resistance (ESR). Assuming a

capacitor with zero ESR, the minimum capacitance needed for a given ripple can be calculated by:

(6)

using:

(7)

Due to its low ESR, Vripple_ESR can be neglected for ceramic capacitors, but must be considered if tantalum or

electrolytic capacitors are used.

Care must be taken when evaluating a ceramic capacitors derating under dc bias, aging and AC signal. For

example, larger form factor capacitors (in 1206 size) have a self resonant frequencies in the range of the

switching frequency. So the effective capacitance is significantly lower. The DC bias can also significantly reduce

capacitance. Ceramic capacitors can loss as much as 50% of its capacitance at its rated voltage. Therefore,

leave the margin on the voltage rating to ensure adequate capacitance at the required output voltage.

The capacitor in the range of 1mF to 4.7mF is recommended for input side. The output requires a capacitor in the

range of 1mF to 10mF. The output capacitor affects the loop stability of the boost regulator. If the output capacitor

is below the range, the boost regulator can potentially become unstable.

The popular vendors for high value ceramic capacitors are:

TDK (http://www.component.tdk.com/components.php)

Murata (http://www.murata.com/cap/index.html)

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