RT8494

3

DS8494-01 November 2015

www.richtek.com

©

Copyright 2015 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

Functional Pin Description

Pin No.

Pin Name

Pin Function

1

RSET

2

ISW

External MOSFET Switch Current Sense. Connect the current sense resistor

between external N-MOSFET switch and the ground.

3

ISP

LED Current Sense Amplifier Positive Input with Common Mode up to 90V.

4

ISN

LED Current Sense Amplifier Negative Input. Voltage threshold between ISP and

ISN is 190mV with common mode voltage up to 90V.

5

VC

PWM Control Loop Compensation.

6

ACTL

Analog Dimming Control. The effective programming voltage range of the pin is

between 0.2V and 1.2V.

7

DCTL

By adding a 0.47

F filtering capacitor on ACTL pin, the PWM dimming signal on

DCTL pin can be averaged and converted into analog dimming signal on the ACTL

pin.

8

SS

Soft-Start Time Setting. A capacitor of at least 10nF is required for proper soft-start.

9

EN

Enable Control Input (Active High). When this pin voltage is low, the chip is in

shutdown mode.

10

OVP

Over-Voltage Protection. The PWM converter turns off when the voltage of the pin

goes to higher than 1.18V.

11

VCC

Power Supply of the Chip. For good bypass, a low ESR capacitor is required.

12

GND

Ground. The Exposed Pad must be Soldered to a Large PCB and Connected to

GND for Maximum Power Dissipation.

13

GBIAS

Internal Gate Driver Bias. A good bypass capacitor is required.

14

GATE

External MOSFET Switch Gate Driver Output.

Figure 3. Analog Dimming in Buck-Boost Configuration

RT8494

L1

ISN

ISP

VCC

EN

5V

22µH

1µF

11

9

SS

VC

0.1µF

3.3nF

10k

5

8

GND

OVP

R1

R2

GATE

ISW

DCTL

Analog

Dimming

7

ACTL

6

RSET

14

2

10

1

3

4

12

GBIAS

13

1µF

D1

LEDs

M1

0.05

4.5V to 36V

0.47

10µF

90V (max)