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TYPICAL APPLICATION USING 2 WHITE LEDs AND 6 GREEN LEDs FOR LCD BACKLIGHT AND

Rg +

V

FLEDD1 *

V

Fg

Ig

VIN

C1+

C1−

C2+

C2−

EN1

EN2

GND

VOUT

D1

D2

D3

D4

D5

ISET

0.47 mF

0.47 mF

1 mF

1 mF

VIN = 2.9 V

to 6.5 V

6 Green

LEDs With

5 mA Each

2 White

LEDs With

30 mA Each

5.4 kW

Sets Current to 30 mA

Per Current Sink

(With EN2 = EN1 = 1)

PGND

PROPOSED LAND PATTERN FOR PCB PRODUCTION

PHOTO FLASH APPLICATIONS

TPS60230

SLVS516A – MAY 2004 – REVISED JUNE 2004

APPLICATION INFORMATION (continued)

KEYBOARD LIGHTING

The TPS60230 can be used to power any kind of LED. It is also possible to mix white LEDs with color LEDs

which have a lower forward voltage. The LED with the highest forward voltage (typically the white LED) has to be

connected to D1, because the output voltage of the charge pump is regulated in such a way to keep the voltage

drop from D1 to GND at 400mV (with EN1 = EN2 = 1). Therefore the output voltage of the charge pump is

regulated to:

Resistor Rg is used to provide current sharing between the 6 green LEDs. The upper value is calculated using:

Figure 14. LED Connections for LCD Backlight and Keyboard Lighting

Refer to the application note SLUA271 for the proposed land pattern of the QFN package.

The TPS60230 can be used to power one or more white LEDs for photo flash applications. These applications

usually require a certain current for a short period of time. The photo flash is typically turned on for 100 ms to

500 ms and turned off for a longer period of time. For such applications, when the TPS60230 is not turned on

continuously, the device can support an output current of 150 mA. See Figure 5 for the input voltage needed for

a certain LED forward voltage and LED current.

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