ADP8860ACBZ-R7 datasheet(18/52 Pages) AD

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ADP8860

Rev. 0 | Page 18 of 52

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

off when BL_EN = 0.

MAX

BACKLIGHT

CURRENT

BL_EN = 1

BL_EN = 0

Figure 32. Backlight Turn On/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

BACKLIGHT

CURRENT

BL_EN = 1 DIM_EN = 1

DIM_EN = 0 BL_EN = 0

Figure 33. Backlight Turn On/Dim/Turn Off

The maximum and dim settings can be set between 0 mA and

30 mA; therefore, it is possible to program a dim setting that is

greater than a maximum setting. For normal expected opera-

tion, 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 timer 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 34. 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 timer 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

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

machine clears the BL_EN bit, and the backlight turns off.

MAX

BL_EN = 1 BL_EN = 0

BACKLIGHT

CURRENT

OFF TIMER

RUNNING

SET BY USER

SET BY INTERNAL STATE MACHINE

Figure 35. Off Timer

The backlight can be turned off at any point during the off

timer countdown by clearing BL_EN.

The dim timer and off timer can be used together for sequential

maximum-to-dim-to-off functionality. With both the dim and

off timers programmed, if BL_EN is asserted, the backlight

turns on to its maximum setting, and when the dim timer

expires, the backlight changes to its dim setting. When the off

timer expires, the backlight turns off.

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