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OUT

2

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[ A

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LM4510

www.ti.com

SNVS533C – SEPTEMBER 2007 – REVISED MAY 2013

To prevent loss of regulation, ensure that the NMOS power switch current limit is greater than the worst-case

peak inductor current in the target application.

Also make sure that the inductor saturation current is greater than the peak inductor current under the worst-case

load transient, high ambient temperature and startup conditions. Refer to Table 2 for suggested inductors.

Table 2. Suggested Inductors and Their Suppliers

Model

Vendor

Dimensions LxWxH (mm)

D.C.R (max)

DO3314-472ML

COILCRAFT

3.3mm x 3.3mm x 1.4mm

320 m

Ω

DO3316P-472ML

COILCRAFT

12.95mm x 9.4mm x 5.4mm

18 m

Ω

INPUT CAPACITOR SELECTION

Due to the presence of an inductor, the input current waveform is continuous and triangular. So the input

capacitor is less critical than output capacitor in boost applications. Typically, a 4.7

μF to 10 μF ceramic input

capacitor is recommended on the VIN pin of the IC.

The RMS current in the input capacitor is given by the following equation:

(6)

The input capacitor should be capable of handling the RMS current.

OUTPUT CAPACITOR SELECTION

The output capacitor in a boost converter provides all the output current when the switch is closed and the

inductor is charging. As a result, it sees very large ripple currents.

A ceramic capacitor of value 4.7

μF to 10 μF is recommended at the output. If larger amounts of capacitance are

desired for improved line support and transient response, tantalum capacitors can be used.

The RMS current in the output capacitor is given by the following equation:

(7)

The output capacitor should be capable of handling the RMS current.

The ESR and ESL of the output capacitor directly control the output ripple. Use capacitors with low ESR and ESL

at the output for high efficiency and low ripple voltage. The output capacitor also affects the soft-start time (See

SOFT-START FUNCTION AND SOFT-START CAPACITOR SELECTION). Table 3 shows suggested input and

output capacitors.

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