RT8284

2

DS8284-01 March 2011

www.richtek.com

Functional Pin Description

Pin No.

SOP-8

(Exposed Pad)

SOP-8

Pin Name

Pin Function

1

1

BOOT

Bootstrap for High-Side Gate Driver. Connect a 10nF or greater

ceramic capacitor from BOOT to SW pins.

2

2

VIN

Input Supply Voltage, 4.5V to 23V. Must bypass with a suitably large

ceramic capacitor.

3

3

SW

Phase Node. Connect this pin to external L-C filter.

4,

9 (Exposed Pad)

4

GND

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

connected to GND for maximum power dissipation.

5

5

FB

Feedback Input Pin. This pin is connected to the converter output. It

is used to set the output of the converter to regulate to the desired

value via an internal resistive divider. For an adjustable output, an

external resistive divider is connected to this pin.

6

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

7

EN

Enable Input pin. A logic high enables the converter; a logic low

forces the RT8284 into shutdown mode reducing the supply current

to less than 3

μA. Attach this pin to VIN with a 100kΩ pull up resistor

for automatic startup.

8

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

R2 (k

Ω)

L (

μH)

8

76.8

10

27

3.3

22

22 x 2

5

45.3

10

20

3.3

15

22 x 2

3.3

26.1

10

13

3.3

10

22 x 2

2.5

16.9

10

9.1

3.3

6.8

22 x 2

1.8

9.53

10

5.6

3.3

4.7

22 x 2

1.2

3

10

3.6

3.3

3.6

22 x 2

Recommended Component Selection

VIN

EN

GND

BOOT

FB

SW

7

5

2

3

1

L

10µH

10nF

22µF x 2

R1

26.1k

R2

10k

3.3V/2A

10µF

4.5V to 23V

RT8284

SS

8

COMP

3.3nF

13k

Open

6

4, 9 (Exposed Pad)

0.1µF