LTC3421

14

3421f

5V Applications

When the output voltage is programmed above 4.3V it is

necessary to add a Schottky diode either from SW to

acceptable peak voltage on SW. The Schottky to the

output will provide a peak efficiency improvement but will

negate the output disconnect feature. If output disconnect

is required, the Schottky to an active snubber network is

suggested as shown in Figure 4.

Figure 4. Lithium-Ion to 5V at 1A Application with an Active Snubber Circuit

TYPICAL APPLICATIO

OUTPUT CURRENT (mA)

30

90

100

20

10

80

50

70

60

40

0.1

10

100

1000

3421 G03

0

1

Burst Mode

OPERATION

Li-Ion to 5V Efficiency

SHDN

ENB

LBI

LBO

SYNC

FB

BURST

SW SW

L1

3

µH

SW

18

17

19

20

1

24

9

13

12

11

10

5

6

8

7

22

23

3

4

221

14

15

16

SS

GND

LTC3421

C2

0.1

µF

C3

0.1

µF

C4

470pF

C5*

22

µF

×2

C6*

1

µF

C1*

10

µF

2.7V TO

4.2V

Li-Ion

R2

28k

R3

10k

R4

100k

R5

1.13M

M1

D1*

5V

1A

R6

365k

3421 F04

R1

60k

*LOCATE COMPONENTS CLOSE TO PINS

C1: TAIYO YUDEN JMK212BJ106MM

C5: TAIYO YUDEN JMK325BJ226MM

PGND PGND PGND

+

D1: MOTOROLA MBR0520L

L1: SUMIDA CDRH6D28-3R0

M1: ZETEX ZXM61P025

Figure 3

1

–

+

1.22V

3421 F03

R2

R1

ERROR

AMP

FB

24

APPLICATIO S I FOR ATIO