SP6682 datasheet(7/13 Pages) EXAR

7 / 13 page

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Rev. 2.0.0

different applications, as shown in figures 12-

14.

Figure 12 shows a circuit using the SP6682 to

drive discrete white LEDs as a current source.

Fig. 12: Driving Discrete White LEDs as Current Source

The current in one white LED current is set by

the ratio of the feedback pin voltage (306mV)

and the bias resistor RB. To set the operating

current, RB can be selected by:

LED

The current of the remaining white LEDs is set

according to the similarity of the white LEDs.

A 3-wire white LED module with internal series

resistors as shown in figure 13 can also be

driven in this way.

Fig. 13: 3-Wire White LED Module

In Figure 14, the SP6682 was used to drive a

2-wire white LED module without internal

series resistors as a current source. The bias

resistor RB is selected to regulate the total

current of the white LED module in-stead of

the current of single LED as in Figure 12.

Fig. 14: Driving 2-Wire White LED Module

as Current Source

In this application, the bias resistor can be

selected by:

)

(TOTAL

LED

Where ILED(TOTAL) is the total operating current

of all the white LEDs.

To use the SP6682 as a voltage source for

fixed voltage applications, a voltage divider is

needed to program the ouput voltage, as

shown in Figure 15.

Fig. 15: Driving 2-Wire White LED Module

as Voltage Source

The output voltage is set by the ratio of the

two resistors and the feedback control voltage

as shown by:

OUT

⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

PROGRAMMING THE OPERATING MODE

SP6682 can automatically change from X1.5

mode to X2 mode for highest efficiency. To

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