ADP8863 Analog Devices, ADP8863 Datasheet - Page 17

• Manufacturer Part Number: ADP8863
• Description: Charge Pump, 7-Channel Fun Lighting LED Driver
• Manufacturer: Analog Devices

Specifications of ADP8863

• Vin Range: 2.5 to 5.5V
• Vout (v): 4.3 to 5.5
• Synchronous: No
• Package: 20-Lead LFCSP,20-Lead WLCSP
• Led Configuration: Parallel
• Topology: Capacitive
• I2c Support: Yes
• Max Iout (ma): 60mA
• Brightness Control: I2C
• Peak Efficiency (%): 89%
• Switching Frequency: 1.32MHz
• Over Volt Protection (v): 5V

starts counting. When the off timer expires, the internal state
machine clears the BL_EN bit, and the backlight turns off.
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, and BL_EN 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.
FADE OVERRIDE
A fade override feature (FOVR in Register CFGR (0x04)) enables
the host to override the preprogrammed fade in or fade out
settings. If FOVR is set and the backlight is enabled in the
middle of a fade out process, the backlight instantly (within
approximately 100 ms) returns to its maximum setting. Alter-
natively, if the backlight is fading in, reasserting BL_EN overrides
the programmed fade in time, and the backlight instantly goes
to its final fade value. This is useful for situations in which a key
is pressed during a fade sequence. However, if FOVR is cleared
and the backlight is enabled in the middle of a fade process, the
backlight gradually brightens from where it was interrupted (it
does not go down to 0 and then comes back on).
BACKLIGHT
MAX
DIM
CURRENT
MAX
SET BY USER
SET BY INTERNAL STATE MACHINE
BACKLIGHT
CURRENT
SET BY USER
SET BY INTERNAL STATE MACHINE
Figure 38. Dim and Off Timers Used Together
BL_EN = 1
DIM TIMER
RUNNING
Figure 37. Off Timer
BL_EN = 1 BL_EN = 0
DIM_EN = 1
OFF TIMER
RUNNING
OFF TIMER
RUNNING
BL_EN = 0
Rev. A | Page 17 of 52
AMBIENT LIGHT SENSING
The ADP8863 integrates two ambient light sensing compara-
tors. One of the ambient light sensing comparator pins
(CMP_IN) is always available. The second pin (D6) has an
ambient light sensor comparator (CMP_IN2) that can be
activated rather than connecting an LED to D6. Activating
the CMP_IN2 function of the pin is accomplished through the
CMP2_SEL bit in Register CFGR. Therefore, when the CMP2_
SEL bit is set to 0, Pin D6 is programmed as a current sink.
When the CMP2_SEL bit is set to 1, Pin D6 becomes the input
for a second phototransistor.
These comparators have two programmable trip points (L2 and
L3) that select one of the three backlight operation modes
(daylight, office, and dark) based on the ambient lighting
conditions.
The L3 comparator controls the dark-to-office mode transition.
The L2 comparator controls the office-to-daylight transition
(see Figure 40). The currents for the different lighting modes
are defined in the BLMXx and BLDMx registers (see the
Backlight Operating Levels Section).
Each light sensor comparator uses an external capacitor together
with an internal reference current source to form an analog-to-
digital converter (ADC) that samples the output of the external
photosensor. The ADC result is fed into two programmable trip
comparators. The ADC has an input range of 0 μA to 1080 μA
(typical).
BACKLIGHT
MAX
Figure 40. Light Sensor Modes Based on the Detected Ambient Light Level
CURRENT
BL_EN = 1
0 LUX
0A
(REASSERTED)
OVERRIDDEN
Figure 39. Fade Override Function (FOVR Is High)
BL_EN = 1
FADE-IN
L2_OUT = 1
L3_OUT = 1
DARK
L3
BL_EN = 0
BRIGHTNESS
L2_OUT = 1
L3_OUT = 0
OFFICE
OVERRIDDEN
FADE-OUT
BL_EN = 1
L2
BL_EN = 0
DAYLIGHT
L2_OUT = 0
L3_OUT = 0
ADP8863