ADP8863ACPZ-R7 datasheet(16/48 Pages) AD

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ADP8863

Rev. 0 | Page 16 of 48

BACKLIGHT OPERATING LEVELS

Backlight brightness control operates at three distinct levels:

daylight (L1), office (L2), and dark (L3). The BLV bits in

operates. These bits can be changed manually or, if in automatic

mode (CMP_AUTOEN is set high in Register 0x01), by the

ambient light sensor (see the Ambient Light Sensing section).

By default, the backlight operates at daylight level (BLV = 00),

where the maximum brightness is set using Register 0x09

(BLMX1). A daylight dim setting can also be set using Register

0x0A (BLDM1). When operating at office level (BLV = 01), the

backlight maximum and dim brightness settings are set using

operating at the dark level (BLV = 10), the backlight maximum

and dim brightness settings are set using Register 0x0D (BLMX3)

and Register 0x0E (BLDM3).

DAYLIGHT (L1)

OFFICE (L2)

DARK (L3)

BACKLIGHT OPERATING LEVELS

DAYLIGHT_DIM

DAYLIGHT_MAX

OFFICE_MAX

DARK_MAX

DARK_DIM

OFFICE_DIM

30mA

Figure 32. Backlight Operating Levels

BACKLIGHT TURN ON/TURN OFF/DIM

With the device in active mode (nSTBY = 1), the backlight can

be turned on using the BL_EN bit in Register 0x01. Before

turning on the backlight, select the level (daylight (L1), office

(L2), or dark (L3)) to operate in and ensure that maximum and

dim settings are programmed for that level. The backlight turns

on when BL_EN = 1. The backlight turns off when BL_EN = 0.

MAX

BL_EN = 1

BL_EN = 0

BACKLIGHT

CURRENT

Figure 33. Backlight Turn On/Turn Off

While the backlight is on (BL_EN = 1), the user can change to

the dim setting by programming DIM_EN = 1 in Register 0x01.

If DIM_EN = 0, the backlight reverts to its maximum setting.

MAX

DIM

BL_EN = 1 DIM_EN = 1

DIM_EN = 0 BL_EN = 0

BACKLIGHT

CURRENT

Figure 34. Backlight Turn On/Dim/Turn Off

The maximum and dim settings can be set from 0 mA to 30 mA;

therefore, it is possible to program a dim setting that is greater

than a maximum setting. For normal expected operation,

ensure that the dim setting is programmed to be less than the

maximum setting.

AUTOMATIC DIM AND TURN OFF TIMERS

The user can program the backlight to dim automatically by

using the DIMT bits in Register 0x07. The dim timer has 127

settings ranging from 1 sec to 127 sec. Program the dim timer

(DIMT) before turning on the backlight. If BL_EN = 1, the

backlight turns on to its maximum setting and the dim timer

starts counting. When the dim timer expires, the internal state

machine sets DIM_EN = 1, and the backlight enters its dim

setting.

MAX

DIM

BL_EN = 1

BL_EN = 0

DIM_EN = 1

DIM_EN = 0 DIM_EN = 1

BACKLIGHT

CURRENT

DIM TIMER

RUNNING

DIM TIMER

RUNNING

SET BY USER

SET BY INTERNAL STATEMACHINE

Figure 35. Dim Timer

If the user clears the DIM_EN bit, the backlight reverts to its

maximum setting and the dim timer begins counting again.

When the dim timer expires, the internal state machine again

sets DIM_EN = 1, and the backlight enters its dim setting. The

backlight can be turned off at any point during the dim timer

countdown by clearing BL_EN.

The user can also program the backlight to turn off automati-

cally by using the OFFT bits in Register 0x06. The off timer has

127 settings ranging from 1 sec to 127 sec. Program the off

timer (OFFT) before turning on the backlight. If BL_EN = 1,

the backlight turns on to its maximum setting and the off timer

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