RT9005A/B

Preliminary

2

DS9005A/B-01 September 2007

www.richtek.com

Typical Application Circuit

Functional Pin Description

Pin No.

Pin Name

Pin Function

1

BP

Noise Reduction. Connecting a 10nF capacitor to GND to reduce output noise.

7,

Exposed Pad (9)

GND

Common Ground (T he exposed pad must be soldered to a large PCB and

connected to GND for maximum power dissipation). The GND pad are a should be

as large as possible and using many vias to conduct the heat into the buried GND

plate of PCB layer.

2

VIN1

Linear Regulator Power Input Voltage.

3

VIN2

Input voltage which supplies current to the output pin. Connect this pin to a

well-decoupled supply voltage. To prevent the input rail from dropping during large

load transient, a large, low ESR capacitor is recommended to use. The capacitor

should be placed as close as possible to the VIN2 pin.

4

VCNTL

VCNTL supplies the internal control circuitr y and provides the drive voltage. The

driving capability of output current is proportioned to the VCNTL. Connect this pin

to 3.3V bias supply to handle large output current with at least 10uF capacitor from

this pin to GND.

5

VREFEN

Reference voltage input and active low VOUT2 shutdown control pin. Two resistors

dividing down the VIN voltage on the pin to create the regulated output voltage.

Pulling the pin to ground turns off the device by an open-drain, such as 2N7002,

signal N-MOSFET.

6

VOUT2

Regulator Output. VOUT2 is regulated to REFEN voltage that is used to terminate

the bus resistors. It is capable of sinking and sourcing current while regulating the

output rail. To maintain adequate large signal transient response, typical value of

1000

μF AL electrolytic capacitor with 10μF ceramic capacitors are recommended to

8

VOUT1

Regulator 2.5V/1.8/1.5V Output.

Note : If there is any application need to use 10

eletrolytic capacitor).

VIN1

VREFEN

GND

VOUT2

RT9005A/B

EN

2N7002

R1

R2

GND

VOUT1

7,

Exposed Pad(9)

3

5

8

6

BP

1

VIN2

VCNTL

2

4

2.2uF

10nF

2.2uF

1uF

470uF

47uF

470uF