RT8280

2

DS8280-02 March 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 Power. 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

GND with a suitably large capacitor to eliminate noise on the input to the IC.

3

SW

Switch Node. 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. Drive FB with a

resistive voltage divider from the output voltage.

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 off. For

automatic startup, leave EN unconnected.

8

RT

Oscillator Resistor Input. Connecting a resistor to ground from this pin sets the

switching frequency.

R1 (k

Ω)

R2 (k

Ω)

L (

μH)

10

115

10

68

0.82

8.2

22

8

91

10

51

1

6.8

22

5

52.3

10

36

1.2

4.7

22

3.3

31.6

10

24

1.8

2.2

22

2.5

21.5

10

18

2.2

2

22

1.8

12.4

10

13

2.2

1.5

22

1.5

8.87

10

12

2.2

1.5

22

1.2

4.99

10

9

1.8

1

22

Typical Application Circuit

4.5V to 24V

NC

VIN

EN

GND

BOOT

FB

SW

7

5

2

3

1

L

2.2µH

10nF

22µF

R1

31.6k

R2

10k

3.3V/3A

10µF

Chip Enable

RT8280

B330A

RT

8

24k

COMP

1.8nF

24k

6

4,

9 (Exposed Pad)