LP3954TLXSLASHNOPB datasheet(37/60 Pages) TI1

37 / 60 page

LP3954

www.ti.com

SNVS340D – JUNE 2005 – REVISED MARCH 2013

OUTPUT DIODE, DOUT

A Schottky diode should be used for the output diode. To maintain high efficiency the average current rating of

the schottky diode should be larger than the peak inductor current (1A). Schottky diodes with a low forward drop

and fast switching speeds are ideal for increasing efficiency in portable applications. Choose a reverse

breakdown of the schottky diode larger than the output voltage. Do not use ordinary rectifier diodes, since slow

switching speeds and long recovery times cause the efficiency and the load regulation to suffer.

INDUCTOR, L1

The LP3954’s high switching frequency enables the use of the small surface mount inductor. A 4.7 µH shielded

inductor is suggested for 2 MHz operation, 10 µH should be used at 1 MHz. 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 SW pin as close

to the IC as possible.

LIST OF RECOMMENDED EXTERNAL COMPONENTS

Symbol

Symbol Explanation

Value

Unit

Type

CVDD1

C between VDD1 and GND

100

Ceramic, X7R / X5R

CVDD2

C between VDD2 and GND

100

Ceramic, X7R / X5R

CVDDIO

C between VDDIO and GND

100

Ceramic, X7R / X5R

CVDDA

C between VDDA and GND

µF

Ceramic, X7R / X5R

COUT

C between FB and GND

µF

Ceramic, X7R / X5R, 10V

CIN

C between battery voltage and GND

µF

Ceramic, X7R / X5R

LBOOST

L between SW and VBAT at 2 MHz

4.7

µH

Shielded,low ESR, Isat 1A

CVREF

C between VREF and GND

100

Ceramic, X7R

CVDDIO

C between VDDIO and GND

100

Ceramic, X7R

RFLASH

R between IFLASH and GND

1.2

Ω

±1%

RRBG

R between IRGB and GND

5.6

Ω

±1%

RRT

R between IRT and GND

Ω

±1%

DOUT

Rectifying Diode (Vf at maxload)

0.3

Schottky diode

CASE

C between Audio input and ASE

100

Ceramic, X7R / X5R

LEDs

User defined

DLIGHT

Light Sensor

TDK BSC2015

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