ADP8863ACPZ-R7 datasheet(14/48 Pages) AD

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ADP8863

Rev. 0 | Page 14 of 48

LED GROUPINGS

Each LED can respond individually or be grouped together

into the backlight controls. By default, all LEDs are set to be

part of the backlight. This is changed by setting Bits[6:0] in

be enabled individually in Register 0x10. They can also all be

enabled simultaneously via the SIS_EN bit in Register 0x01.

Any LEDs configured for the backlight can only be enabled

via the BL_EN bit in Register 0x01.

LED CURRENT SETTINGS

Any of the LED outputs (Pin D1 to Pin D7) can be used to

drive any color of LED at 0 mA to 30 mA, provided that the

LED’s Vf is less than 4.1 V. Additionally, the D7 sink can regu-

late up to 60 mA. The current settings are determined by a

7-bit code programmed by the user into Register 0x14 through

allows the user to set the LED to one of 128 different levels.

The ADP8863 can implement two distinct algorithms to

achieve a linear or a nonlinear relationship between input

code and diode output current. The law and SC_LAW bits

in Register 0x04 and Register 0x0F, respectively, are used to

change between these algorithms.

By default, the ADP8863 uses a linear algorithm (law and

SC_LAW = 00), where the LED current increases linearly for

a corresponding increase in input code. LED current (in

milliamperes) is determined by the following equation:

LED Current (mA) = Code × (Full-Scale Current/127)

(2)

where:

Code is the input code programmed by the user.

Full-Scale Current is the maximum sink current allowed per

LED (typically 30 mA).

The ADP8863 can also implement a nonlinear (square

approximation) relationship between input code and LED

current. In this case (law and SC_LAW = 01, 10, or 11), the LED

current (in milliamperes) is determined by the following

equation:

127

)

(

⎟

⎠

⎞

⎜

⎝

⎛

−

Current

Scale

Full

Code

Current

LED

(3)

Figure 28 shows the LED current level vs. input code for both

the linear and square law algorithms.

032

CODE

LINEAR

SQUARE

Figure 28. LED Current vs. Input Code

AUTOMATED FADE IN AND FADE OUT

The LED drivers are easily configured for automated fade in

and fade out. Sixteen fade in and fade out rates can be selected

via the I2C interface. Fade in and fade out rates range from

0.0 sec to 5.5 sec (per full-scale current, either 30 mA or 60 mA).

The backlight LEDs have separate fade in and fade out time

controls from the independent sink LEDs.

Table 5. Available Fade In and Fade Out Rates

Code

Fade Rate (in sec per Full-Scale Current)

0000

0.0 (disabled)

0001

0.3

0010

0.6

0011

0.9

0100

1.2

0101

1.5

0110

1.8

0111

2.1

1000

2.4

1001

2.7

1010

3.0

1011

3.5

1100

4.0

1101

4.5

1110

5.0

1111

5.5

The fade profile is based on the transfer law selected (linear,

square, Cubic 10, or Cubic 11) and the delta between the actual

current and the target current. Smaller changes in current

reduce the fade time. For linear and square law fades, the fade

time is given by

Fade Time = Fade Rate × (Code/127)

(4)

where the Fade Rate is shown in Table 5.

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