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Date: 5/5/04

SP6682 High Efficiency Charge Pump Regulator for White LEDs

© Copyright 2004 Sipex Corporation

encing high input voltages. Another important

operation of this block is the PWM/EN dim-

ming control, which is implemented in the delay

of each pump driver, so that the enable high

pulse width is proportional to the delay of the

individual pump switches.

306mV reference voltage is compared to feed-

1

8

5

Rb

SP6682

Rb

2.2uF

GND

FB

V

OUT

Figure 9. Driving discrete white LEDs as current source

Configuring the SP6682 as Voltage or

Current Source

The white LED load configuration used by

customers can be discrete white LEDs or a white

LED module. Inside the white LED module,

there may or may not be resistors in series with

the white LEDs. According to the different

application requirements, the SP6682 can be

configured as either a voltage source or a current

source to provide solutions for these different

applications, as shown in figure 9~12. Figure 9

shows using the SP6682 to drive discrete white

LEDs as a current source.

The current in one white LED current is set by

the ratio of the feedback pin voltage (306mV)

3-wire W-LED module

Anode

FB

GND

Fig 10. 3-wire white LED module

The current of the remaining white LEDs is set

according to the similarity of the white LEDs. 3-

wire white LED module with internal series

resistors as shown in figure 10 can also be driven

in this way.

GND

V

OUT

Anode

5

V

FB

Rb

SP6682

Cathode

8

2-wire W-LED module

1

Figure 11. Driving 2-wire white LED module as current

source

OPERATION: Continued

back output voltage to control the Vout needed

for the application. Output current is set by a

bias resistor from FB pin to GND pin chosen by

the relationship:

In figure 11, SP6682 was used to drive a 2-wire

white LED module without internal series resis-

selected to regulate the total current of the white

LED module instead of the current of single

LED as in figure 9.

APPLICATION INFORMATION