RT9301 datasheet(8/9 Pages) RICHTEK

8 / 9 page

RT9301

DS9301-02

March 2007

www.richtek.com

Layout Consideration

For best performance, careful PCB layout is necessary.

Place all peripheral components as close to the IC as

possible. A short connection is highly recommended. The

following guidelines should be strictly followed when

designing a PCB layout for the RT9301.

1. All the traces of LED and VIN pin running from chip to

LEDs should be wide and short to reduce the parasitic

connection resistance.

2. Input capacitor (CIN) must be placed close to LEDs and

connected to ground plane. The anodes of LEDs must

be connected to CIN, not battery directly.

3. Current setting resistors RSET should be placed as close

to the chip as possible.

4. The GND should be connected to a strong ground plane

for heat sinking and noise protection.

5. The current setting resistors should be placed as close

to the IC as possible.

The maximum power dissipation depends on operating

ambient temperature for fixed TJ (MAX) and thermal resistance

θJA . For RT9301 packages, the Figure 6 of derating curves

allows the designer to see the effect of rising ambient

temperature on the maximum power allowed.

Figure 6. Derating Curves for RT9301 Packages

100

150

200

250

300

350

400

450

500

100

120

140

Ambient Temperature (°C)

Single Layer PCB

Battery

Ground Plane

All the traces of LED and V

running from

chip to LEDs should be wide and short to

reduce the parasitic connection resistance.

Input capacitor (C

IN) should

be placed close to LEDs

Pin and connected to

ground plane. The Anodes

of LEDs must connect to

IN, not battery directly.

The GND should be connected to a strong

ground plane for heat sinking and noise

protection.

ISET3

VIN

GND

LED3

LED2

LED1

ISET1

ISET2

Figure 7. PCB Layout Guide

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