RT9300A/B

Preliminary

2

DS9300A/B-02 March 2007

www.richtek.com

Function Block Diagram

Functional Pin Description

Pin

Name

Function

1

EN

Chip Enable (Active High).

2

GND

Ground

3

LED4

LED4 Cathode Connection. Current flowing into LED4 is Constant. (20mA/15 mA)

LED4 is High Impedance when EN is Low.

4

LED3

LED3 Cathode Connection. Current flowing into LED3 is Constant. (20mA/15 mA)

LED3 is High Impedance when EN is Low.

5

LED2

LED2 Cathode Connection. Current flowing into LED2 is Constant. (20mA/15 mA)

LED2 is High Impedance when EN is Low.

6

LED1

LED1 Cathode Connection. Current flowing into LED1 is Constant. (20mA/15 mA)

LED1 is High Impedance when EN is Low.

+

-

Current Source

UVLO

Bandgap

OTP

LED1

LED2

LED3

LED4

EN

I

REF

V

REF

Figure 2. Application circuit for keypad.

LED4

LED3

LED2

LED1

GND

EN

PWM

V

IN

6

5

43

1

2

RT9300A/B

C

0.1uF

Keypad

LED