LT3467/LT3467A

7

3467afe

APPLICATIONS INFORMATION

GND

SW

SS

FB

2.6V TO 4.2V

D1

L1

2.7μH

R1

402k

LT3467

3467 TA05a

C2

15μF

C4

3.3pF

C1

4.7μF

R2

133k

5V

C1, C2: X5R OR X7R, 6.3V

D1: ON SEMICONDUCTOR MBRM120

L1: SUMIDA CR43-2R7

SHDN

OFF ON

C3

0.047μF

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

Table 1. Inductor Manufacturers

Sumida

(847) 956-0666

www.sumida.com

TDK

(847) 803-6100

www.tdk.com

Murata

(714) 852-2001

www.murata.com

FDK

(408) 432-8331

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

1V/DIV

0.5A/DIV

0.1ms/DIV

3467 AI01

Supply Current of Figure 2 During Start-Up

with a 47nF Soft-Start Capacitor

1V/DIV

0.5A/DIV

0.5ms/DIV

3467 AI02