RT8288A

2

DS8288A-03

June 2012

www.richtek.com

©

Copyright

2012 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

Function Pin Description

Pin No.

Pin Name

Pin Function

1

VIN

Supply Input. VIN supplies the power to the IC, as well as the step-down converter

switches. Drive VIN with a 4.5V to 21V power source. Bypass VIN to GND with a

suitably large capacitor to eliminate noise on the input to the IC.

2, 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

BOOT

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

N-MOSFET switch. Connect a 100nF or greater capacitor from SW to BOOT to

power the high side switch.

5

EN

Chip Enable (Active High). For automatic start-up, connect the EN pin to VIN with a

100k

Ω resistor.

6

FB

Feedback Input. FB senses the output voltage to regulate said voltage. Drive FB

with a resistive voltage divider from the output voltage. The feedback threshold is

0.808V.

7

VCC

Bias Supply. Decouple with 0.1

μF to 0.22μF capacitor. The capacitance should be

no more than 0.22

μF.

8,

9 (Exposed Pad)

GND

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

GND for maximum power dissipation.

Table 1. Recommended Components Selection

Typical Application Circuit

R1 (k

Ω)

R2 (k

Ω)

L (

μH)

5

75

14.46

0

4.7

22 x 2

3.3

75

24.32

0

3.6

22 x 2

2.5

75

35.82

0

3.6

22 x 2

1.8

5

4.07

30

2

22 x 2

1.5

5

5.84

39

2

22 x 2

1.2

5

10.31

47

2

22 x 2

1.05

5

16.69

47

1.5

22 x 2

VIN

EN

GND

BOOT

FB

SW

5

6

1

2, 3

4

L

100nF

R2

22µF

RT8288A

8, 9 (Exposed Pad)

R1

VCC

0.1µF

7

Chip Enable