User manual

Input Data Code

(Decimal)

3/256

PWM dimming duty

4/256

5/256

6/256

254

253

255

252

256/256

251

255/256

254/256

253/256

252/256

2/256

(Skipped)1/256

PWM Dimming Control

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Figure 10. PWM dimming duty vs code value of a data byte

In the serial interface mode, the six output channels are grouped into four individual groups. The on duty

of each group is controlled by the value of a specific data byte as listed in the following table:

Output channel Data byte

CH0, CH1 BYTE1

CH2, CH3 BYTE2

CH4 BYTE3

CH5 BYTE4

Because the data width of a data byte is fixed to 8 bits, the step size of the LED current is equal to 1/256

of the full scale current. To allow the use of 0% on duty, the steps 1 and 2 are combined to give a 2/256

on duty. Thus either applying a hexadecimal code 001h or 002h the LM3463 will give a 2/256 on duty. The

dimming duty in the serial interface mode is governed by the following equation:

(5)

Figure 10 shows the relationship of the code value of a data byte and PWM dimming duty.

DC Interface Mode

In the DC interface mode, the on duty of the output channels are adjusted according to the voltage on the

terminals TP12, TP14, TP16 and TP20. In this mode, the six output channels are grouped into four groups

and controlled by the voltage on four terminals individually as listed in the following table:

AN-2255 LM3463 Evaluation Board SNVA642A–May 2012–Revised May 2013

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