RT9287

Preliminary

2

DS9287-01 August 2007

www.richtek.com

Typical Application Circuit

Functional Pin Description

Pin No.

Pin Name

Pin Function

1

VDD1

LDO Power Input Voltage.

2

EN1

LDO Channel 1 Enable. (Active High).

3

EN2

LDO Channel 2 Enable. (Active High).

4

ENB

Boost Enable (Active High). Voltage sensing input to trigger the function of over

voltage protection. Note that this pin is high impedance. There should be a pull

low 100k

Ω resistor connected to GND when the control signal is floating.

5

FB

Boost Feedback Reference Voltage Pin. Series connect a resistor between

WLED and ground as a current sense. Sense the current feedback voltage to

set the current rating.

6

LX

Boost Switch Pin. Connect this Pin to inductor and catch diode. Minimize the

track area to reduce EMI.

7

VDD2

Boost Supply Input Voltage Pin. Bypass 1

μF capacitor to GND to reduce the

input noise.

8

GND

GND pin should be soldered to PCB board and connected to GND.

9

VLDO2

LDO Channel 2 Output Voltage.

10

VLDO1

LDO Channel 1 Output Voltage.

Exposed Pad (11)

GND

The exposed pad must be soldered to a large PCB and connected to GND for

maximum power dissipation.

Ω

>

=

×

+

=

100k

R2

(typ.)

1.235

V

V

R2

R2

R1

V

FB

FB

OUT

EN1

EN2

VLDO1

VLDO1

GND

VDD1

1uF

1uF

1uF

Chip Enable

10

9

8

1

2

3

VDD2

LX

FB

RT9287

ENB

7

4

5

6

+

2.7V to 5.5V

C1

1uF

C2

R2

D1

SS0520

L1

4.7uH to 22uH

R1

910k

105k

12V

1uF/16V