RT9285C

Preliminary

2

DS9285C-00

August 2007

www.richtek.com

Function Pin Description

Pin No.

XDFN/WDFN-8L TSOT-23-6

Pin Name

Pin Function

1,

Exposed Pad (9)

2

GND

connected to GND for maximum power dissipation.

2

1

LX

LX Pin. Connect this Pin to an inductor. Minimize the track area to

reduce EMI.

3

--

NC

No Internal Connection.

4

--

PGND

Power Ground Pin.

5

6

VDD

Supply Input Voltage Pin. Bypass 1uF capacitor to GND to reduce the

input ripple.

6

5

VOUT

Output Voltage pin. The pin internally connects to OVP diode to limit

output voltage while LEDs are disconnected.

7

4

EN

Chip Enable (Active High). Note that this pin has an internal pull-down

resistance around 300k

Ω.

8

3

FB

Feedback Pin. Series connecting a resistor between WLED and ground

as a current sense. Sense the current feedback voltage to set the

current rating.

Typical Application Circuit

LX

GND

VDD

FB

VOUT

RT9285C

EN

C1

1uF

L1

10uH to 22uH

12.5

C2

0.22uF to 1uF

Chip Enable

2.7V to 5.5V

PGND

PGND pin for XDFN/WDFN-8L Packages

Figure 1. Operation of Digital Pulse Dimming Control

15/16 14/16

13/16 12/16

3/16

1/16

2/16

100%

100%

15/16

0

1234

5

14

15

01

EN

Shutdown

Shutdown