RT7253A

2

DS7253A-02 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 17V. Must bypass with a suitably large ceramic

capacitor.

3

SW

Phase 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 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 voltage divider. For an adjustable output, an external resistive

voltage 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

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

RT7253A 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

R2 (k

Ω)

L (

μH)

8

27

3

24

4.7

22

22 x 2

5

62

11.8

18

4.7

15

22 x 2

3.3

75

24

12

4.7

10

22 x 2

2.5

25.5

12

8.2

4.7

6.8

22 x 2

1.5

10.5

12

3.6

4.7

3.6

22 x 2

1.2

12

24

3

4.7

3.6

22 x 2

1

3

12

2.7

4.7

3.6

22 x 2

VIN

EN

GND

BOOT

FB

SW

7

5

2

3

1

L

10µH

100nF

22µF x 2

R1

75k

R2

24k

3.3V/2A

10µF x 2

4.5V to 17V

RT7253A

SS

8

COMP

3.3nF

13k

Open

6

4, 9 (Exposed Pad)

0.1µF