14

LTC3404

3404fb

Figure 8. Single Lithium-Ion to 2.5V/0.3A Regulator from Design Example

2.5V

*

**

***

47pF

10

μF***

CER

6.2

μH*

887k

22

μF**

CER

412k

LTC3404

RUN

GND

8

7

6

5

1

2

3

4

PLL LPF

SYNC/MODE

SW

2.65V

TO 4.2V

TOKO D63LCB A920CY-6R2M

TAIYO-YUDEN CERAMIC JMK325BJ226MM

TAIYO-YUDEN CERAMIC LMK325BJ106MN

3404 F08a

20pF

TYPICAL APPLICATIO S

2.5V

0.6A

10

μF

CER

20pF

887k

22

μF

CER

*

**

***

47pF

4.7

μH*

LTC3404

RUN

GND

8

7

6

5

1

2

3

4

PLL LPF

SYNC/MODE

SW

3V TO 4.2V

TOKO D52LC A914BYW-4R7M

TAIYO-YUDEN CERAMIC JMK325BJ226MM

TAIYO-YUDEN CERAMIC LMK325BJ106MN

3404 TA03

412k

Single Li-Ion to 2.5V/0.6A Regulator

Using All Ceramic Capacitors

OUTPUT CURRENT (mA)

95

90

85

80

75

70

0.1

10

100

1000

3404 F8b

1.0

L = 6.2

μH

APPLICATIO S I FOR ATIO

f = 1.4MHz in equation (3) gives:

L

V

MHz

mA

V

V

H

=

−

⎛

⎝⎜

⎞

⎠⎟

= μ

25

1 4

120

1

25

42

6

.

.(

)

.

.

A 6.2

μH inductor works well for this application. For best

efficiency choose a 1A inductor with less than 0.25

Ω

series resistance.

0.25

Ω. In most applications, the requirements for these

capacitors are fairly similar.

For the feedback resistors, choose R1 = 412k. R2 can

then be calculated from equation (2) to be:

R

V

R

k use

OUT

2

08

1

1 875 5

8

=

−

⎛

⎝⎜

⎞

⎠⎟

=

.

.

;

87k

Figure 8 shows the complete circuit along with its effi-

ciency curve.