RT8250

2

DS8250-05

March 2011

www.richtek.com

Functional Pin Description

Pin No.

Pin Name

Pin Function

1

BOOT

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

from the BOOT pin to SW pin.

2

VIN

Voltage Supply Input. The input voltage range is from 4.5V to 23V. A suitable large

capacitor must be bypassed with this pin.

3

SW

Switching Node. Connect the output LC filter between the SW pin and output load.

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

Output Voltage Feedback Input. The feedback reference voltage is 0.925V

typically.

6

COMP

Compensation Node. This pin is used for compensating the regulation control

loop. A series RC network is required to be connected from COMP to GND. If it is

needed, an additional capacitor should be connected from COMP to GND.

7

EN

Enable Input. A logic high enables the converter, a logic low forces the converter

into shutdown mode reducing the supply current to less than 3

μA. For automatic

startup, connect this pin to VIN with a 100k

Ω pull up resistor.

8

SS

Soft-Start Control Input. The soft-start period can be set by connecting a capacitor

from the SS to GND. A 0.1

μF capacitor sets the soft-start period to 13ms typically.

R1 (k

Ω)

R2 (k

Ω)

L (μH)

15

153

10

30

3.9

33

22 x 2

10

97.6

10

20

3.9

22

22 x 2

8

76.8

10

15

3.9

22

22 x 2

5

45.3

10

13

3.9

15

22 x 2

3.3

26.1

10

6.8

3.9

10

22 x 2

2.5

16.9

10

6.2

3.9

6.8

22 x 2

1.8

9.53

10

4.3

3.9

4.7

22 x 2

1.2

3

10

3

3.9

3.6

22 x 2

Table 1. Recommended Component Selection

Typical Application Circuit

VIN

EN

GND

BOOT

FB

SW

7

5

2

3

1

L1

10µH

10nF

22µFx2

R1

26.1k

R2

10k

3.3V/3A

10µFx2

4.75V to 23V

RT8250

SS

8

0.1µF

COMP

3.9nF

6.8k

NC

6

4,

Exposed Pad(9)

100k