ADP8860 Analog Devices, ADP8860 Datasheet - Page 19

• Manufacturer Part Number: ADP8860
• Description: Charge Pump, 7-Channel Smart LED Driver with I2C Interface
• Manufacturer: Analog Devices

Specifications of ADP8860

• Vin Range: 2.4V to 5.5V
• Vout (v): 4.3 to 5.5
• Synchronous: No
• Package: 20-Lead WLCSP
• Led Configuration: Parallel
• Topology: Capacitive
• I2c Support: Yes
• Max Iout (ma): 60mA
• Brightness Control: I2C
• Peak Efficiency (%): 89%
• Switching Frequency: 1MHz

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 where 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 come back on).
AMBIENT LIGHT SENSING
The ADP8860 integrates two ambient light sensing comparators.
One of the ambient light sensing comparator pins (CMP_IN)
is always available. The second pin (D6/CMP_IN2) can be
activated rather than connecting an LED to D6. Activating
the CMP_IN2 function of the pin is accomplished through
Bit CMP2_SEL in Register CFGR. Therefore, when Bit CMP2_SEL
is set to 0, Pin D6/CMP_IN2 is programmed as a current sink.
When Bit CMP2_SEL is set to 1, Pin D6/CMP_IN2 becomes
the input for a second phototransistor.
MAX
MAX
BACKLIGHT
BACKLIGHT
DIM
CURRENT
CURRENT
BL_EN = 1
SET BY USER
SET BY INTERNAL STATE MACHINE
OVER-RIDDEN
Figure 37. Fade Override Function (FOVR is High)
(RE-ASSERTED)
Figure 36. Dim and Off Timers Used Together
BL_EN = 1
FADE-IN
BL_EN = 1
DIM TIMER
RUNNING
DIM_EN = 1
BL_EN = 0 BL_EN = 1 BL_EN = 0
OFF TIMER
RUNNING
OVER-RIDDEN
FADE-OUT
BL_EN = 0
Rev. 0 | Page 19 of 52
These comparators have two programmable trip points (L2 and
L3) that select among three of the 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 38). 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).
The L2_CMPR detects when the photosensor output has dropped
below the programmable L2_TRP point (Register 0x1D). If this
event occurs, then the L2_OUT status signal is set. L2_CMPR
contains programmable hysteresis, meaning that the photo-
sensor output must rise above L2_TRP + L2_HYS before
L2_OUT clears. L2_CMPR is enabled via the L2_EN bit. The
L2_TRP and L2_HYS values of L2_CMPR can be set between
0 μA and 1080 μA (typical) in steps of 4.3 μA (typical).
The L3_CMPR detects when the photosensor output has
dropped below the programmable L3_TRP point (Register 0x1F).
If this event occurs, the L3_OUT status signal is set. L3_CMPR
SENSOR
OUTPUT
Figure 38. Light Sensor Modes Based on the Detected Ambient Light Level
PHOTO
0 LUX
0A
Figure 39. Ambient Light Sensing and Trip Comparators
L2_OUT = 1
L3_OUT = 1
ADC
DARK
L3
L2_TRIP
L3_TRIP
BRIGHTNESS
SETTINGS
L2_OUT = 1
L3_OUT = 0
FILTER
OFFICE
L2_HYS
L3_HYS
L2
L2_EN
L3_EN
DAYLIGHT
L2_OUT = 0
L3_OUT = 0
ADP8860
L2_OUT
L3_OUT