RT8271

3

DS8271-02 March 2011

www.richtek.com

Functional Pin Description

Pin No.

PMSOP-10

SOP-8

Pin Name

Pin Function

1, 3

--

NC

No Internal Connection.

2

1

BOOT

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

high side N-MOSFET switch. Connect a 10nF or greater capacitor

from SW to BOOT to power the high side switch.

4

2

VIN

step-down converter switches. Bypass VIN to GND with a suitable

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

5

3

SW

Power Switching Output. 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.

6,

11 (Exposed Pad)

4

GND

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

connected to GND for maximum power dissipation.

7

5

FB

Feedback Input. FB senses the output voltage to regulate said

voltage. The feedback reference voltage is 0.92V typically.

8

6

COMP

Compensation Node. COMP is used to compensate the regulation

control loop. Connect a series RC network from COMP to GND to

compensate the regulation control loop. In some cases, an additional

capacitor from COMP to GND is required.

9

7

EN

Enable Input. EN is a digital input that turns the regulator on or off.

Drive EN higher than 1.4V to turn on the regulator, lower than 0.4V to

turn it off. If the EN pin is open, it will be pulled to high by internal

circuit.

10

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 10nF

capacitor sets the soft-start period to 1ms.