RT8274

2

DS8274-01 March 2011

www.richtek.com

Functional Pin Description

Pin No.

Pin Name

Pin Function

1

BOOT

High Side Gate Drive Boost Input. BOOT supplies the drive for the high side

N-MOSFET switch. Connect a 10nF or greater capacitor from SW to BOOT to

power the high side switch.

2

VIN

switches. Bypass VIN to GND with a suitable large capacitor to eliminate noise on

the input to the IC.

3

SW

Power Switching Output. SW is the switching node that supplies power to the

output. Connect the output LC filter from SW to the output load. Note that a

capacitor is required from SW to BOOT to power the high side switch.

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. FB senses the output voltage to regulate said voltage. The

feedback reference voltage is 1.222V typically.

6

COMP

Compensation Node. COMP is used to compensate the regulation control loop.

Connect a series RC network from COMP to GND to compensate the regulation

control loop. In some cases, an additional capacitor from COMP to GND is

required.

7

EN

Enable Input. EN is a digital input that turns the regulator on or off. Drive EN

higher than 1.4V to turn on the regulator, lower than 0.4V to turn it off. If the EN pin

is open, it will be pulled to high by internal circuit.

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 10ms.

R1 (k

Ω)

R2 (k

Ω)

L (

μH)

12

88.7

10

16.9

1.5

22

22

5

30

10

7.5

4.7

15

22

3.3

16.9

10

4.7

4.7

10

22

2.5

10.5

10

3.9

5.6

6.8

22

1.8

4.75

10

3

5.6

4.7

22

Table 1. Recommended Component Selection