LT3467AIS67 Ver la hoja de datos (PDF) - Linear Technology

Número de pieza

componentes Descripción

Fabricante

LT3467AIS67

1.1A Step-Up DC/DC Converter with Integrated Soft-Start

Linear Technology 

LT3467/LT3467A

APPLICATIONS INFORMATION

VIN

2.6V TO 4.2V

C1

4.7μF

OFF ON

C3

0.047μF

L1

2.7μH

D1

VIN

SW

SHDN

LT3467

SS

FB

GND

R1

402k

C4

3.3pF

R2

133k

VOUT

5V

765mA AT VIN = 4.2V,

540mA AT VIN = 3.3V,

360mA AT VIN = 2.6V

C2

15μF

C1, C2: X5R OR X7R, 6.3V

D1: ON SEMICONDUCTOR MBRM120

L1: SUMIDA CR43-2R7

3467 TA05a

Figure 2. Single Li-Ion Cell to 5V Boost Converter (Same as 1st Page Application)

Table 1. Inductor Manufacturers

Sumida

(847) 956-0666

TDK

(847) 803-6100

Murata

(714) 852-2001

FDK

(408) 432-8331

www.sumida.com

www.tdk.com

www.murata.com

www.fdk.co.jp

Soft-Start

The soft-start feature provides a way to limit the inrush

current drawn from the supply upon start-up. An internal

250k resistor charges the external soft-start capacitor

to 1.255V. After the capacitor reaches 0.15V the rate of

voltage rise at the output of the comparator A1 tracks the

rate of voltage rise of the soft-start capacitor. This limits

the inrush current drawn from the supply during start-

up. The soft-start feature plays another important role in

applications where the switch will reach levels of 30V or

higher. During start-up, excessively high switch current,

together with the presence of high voltage can overstress

the switch. A properly used soft-start feature will keep the

switch current from overshooting. This practice will greatly

improve the robustness of such designs. Once the part is

shut down, the soft-start capacitor is quickly discharged

to 0.4V, then slowly discharged through the 250k resistor

to ground. If the part is to be shut down and re-enabled in

a short period of time while soft-start is used, you must

ensure that the soft-start capacitor has enough time to

discharge before re-enabling the part. Typical values of

the soft-start capacitor range from 10nF to 200nF.

Supply Current of Figure 2 During Start-Up

Without Soft-Start Capacitor

VOUT

1V/DIV

ISUPPLY

0.5A/DIV

0.1ms/DIV

3467 AI01

Supply Current of Figure 2 During Start-Up

with a 47nF Soft-Start Capacitor

VOUT

1V/DIV

ISUPPLY

0.5A/DIV

0.5ms/DIV

3467 AI02

3467afe

7

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