RT8293B

2

DS8293B-03

March 2011

www.richtek.com

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 23V. Must bypass with a suitably 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. 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

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

Chip Enable (Active High). A logic low forces the RT8293B into shutdown

mode reducing the supply current to less than 3

µA. Attach this pin to VIN with

a 100k

Ω pull up resistor for automatic startup.

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 13.5ms.

Typical Application Circuit

Ω)

R2 (k

Ω)

Ω)

L (

µH)

µF)

8

27

3

51

2.2

10

22 x 2

5

62

11.8

33

2.2

6.8

22 x 2

3.3

75

24

22

2.2

3.6

22 x 2

2.5

25.5

12

16

2.2

3.6

22 x 2

1.5

10.5

12

10

2.2

2

22 x 2

1.2

12

24

8.2

2.2

2

22 x 2

1

3

12

6.8

2.2

2

22 x 2

Table 1. Recommended Component Selection

VIN

EN

GND

BOOT

FB

SW

7

5

2

3

1

L

3.6

µH

100nF

22

µF x 2

R1

75k

R2

24k

3.3V/3A

10

µF x 2

4.5V to 23V

RT8293B

SS

8

COMP

2.2nF

22k

Open

6

4, 9 (Exposed Pad)

0.1

µF