RT7270

2

DS7270-01

September 2012

www.richtek.com

Copyright

2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

©

Functional Pin Description

Pin No.

Pin Name

Pin Function

1

BOOT

Bootstrap for High Side Gate Driver. Connect a 0.1

μF or greater ceramic

capacitor from BOOT to SW pins.

2

VIN

Input Supply Voltage, 4.5V to 18V. Must bypass with a suitable large ceramic

capacitor.

3

SW

Switch Node. Connect this pin to an external L-C filter.

4,

9 (Exposed Pad)

GND

Ground. The exposed pad must be soldered to a large PCB and connected to

GND for maximum power dissipation.

5

FB

Feedback Input. It is used to regulate the output of the converter to a set value

via an external resistive voltage divider.

6

COMP

Compensation Node. COMP is used to compensate the regulation control

loop. Connect a series RC network from COMP to GND. In some cases, an

additional capacitor from COMP to GND is required.

7

EN

Enable Input Pin. A logic high enables the converter; a logic low forces the IC

into shutdown mode reducing the supply current to less than 3

μA.

8

SS

Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor

from SS to GND to set the soft-start period. A 0.1

μF capacitor sets the

soft-start period to 15.5ms.

Typical Application Circuit

R1 (k

Ω)

R2 (k

Ω)

L (μH)

15

153

10

30

3.9

33

22 x 2

10

97.6

10

20

3.9

22

22 x 2

8

76.8

10

15

3.9

22

22 x 2

5

45.3

10

13

3.9

15

22 x 2

3.3

26.1

10

6.8

3.9

10

22 x 2

2.5

16.9

10

6.2

3.9

6.8

22 x 2

1.8

9.53

10

4.3

3.9

4.7

22 x 2

1.2

3

10

3

3.9

3.6

22 x 2

Table 1. Recommended Component Selection

VIN

EN

GND

BOOT

FB

SW

7

5

2

3

1

L

10µH

0.1µF

22µF x 2

R1

26.1k

R2

10k

3.3V

10µF x 2

4.5V to 18V

RT7270

SS

8

COMP

3.9nF

6.8k

Open

6

4, 9 (Exposed Pad)

0.1µF