LP3936

SNVS259D – NOVEMBER 2003 – REVISED MAY 2013

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INDUCTOR, L

The high switching frequency enables the use of the small surface mount inductor. A 10 µH shielded inductor is

suggested. Values below 4.7 µH should not be used. The inductor should have a saturation current rating higher

than the peak current it will experience during circuit operation (1A). Less than 300 m

Ω ESR is suggested for

high efficiency. Open core inductors cause flux linkage with circuit components and interfere with the normal

operation of the circuit. This should be avoided. For high efficiency, choose an inductor with a high frequency

core material such as ferrite to reduce the core losses. To minimize radiated noise, use a toroid, pot core or

shielded core inductor. The inductor should be connected to the OUT pin as close to the IC as possible.

Examples of suitable inductors are TDK types LLF4017T-100MR90C and VLF4012AT-100MR79 and Coilcraft

type DO3314T-103 (unshielded).

List of Recommended External Components

Symbol

Symbol Explanation

Value

Unit

Type

1

µF

Ceramic, X7R

1

µF

Ceramic, X7R

Output capacitor from FB

10

µF

Ceramic, X7R/Y5V

to GND

Input capacitor from

10

µF

Ceramic, X7R/Y5V

Battery Voltage to GND

1

µF

Ceramic, X7R

Internal LDO output

1

µF

Ceramic, X7R

and GND

RT

Oscillator Frequency Bias

82

k

Ω

Resistor

RDO

DO output pull-up resistor

100

k

Ω

Reference Voltage

100

nF

Ceramic, X7R

and GND

Boost converter inductor

10

µH

Shielded, Low ESR,

0.3

V

Schottky Diode

Maxload

RGB

RGB LED

User Defined

Current Limit Resistors

See the AN-1293 Application Report (SNVA071) for resistor size calculation.

LEDs

White LEDs

(1)

Resistor RT tolerance change will change the timing accuracy of the RGB block. Also the boost converter switching frequency will be

affected.

22

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