ADP8863 Analog Devices, ADP8863 Datasheet - Page 20

• 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

ADP8863
OPERATING LEDS FROM ALTERNATIVE SUPPLIES
For some applications, it is advantageous to operate the LEDs
from a voltage source other than the ADP8863 charge pump
output. For example, it may be possible to operate a red LED
over the entire battery voltage range without any charge pump
boosting. For a charge pump,
Therefore, operating the red LEDs directly from the battery
removes output current of the red LEDs from the charge pump
draw. This in turn reduces the total input current by (Gain − 1) ×
I
However, care must be taken when selecting LEDs to operate
from a different voltage input. Specifically, the voltage source
must at least be able to support the maximum forward voltage
(Vf) of the LED plus the maximum V
Table 1). Additionally, operating an LED from an independent
voltage source may interfere with the ADP8863’s gain selection
algorithm. This algorithm selects the optimal gain for the
charge pump based on all seven diodes. By operating one or
more of the diodes from another supply, the algorithm may not
switch the gain back down to a lower state until the LEDs are
disabled or the part enters standby.
OUT(red)
I
CMP_IN
IN
.
V
=
ALS
nRST
nINT
SDA
SCL
Gain
VIN
SENSOR
BACKLIGHT
PHOTO
1µF
0.1µF
×
I
OUT
D2
D3
GNDx
D4
ADP8863
HR(UP)
Figure 45. Connecting the ADP8863 to an ADP8861 to Power More LEDs
D5
(276 mV, given in
D6
D7
D1
Rev. A | Page 20 of 52
(7)
C1+
C1–
C2+
C2–
VOUT
1µF
C1
1µF
C2
1µF
nRST
nRST
nINT
SDA
SCL
nINT
FUN LIGHTING
SDA
VIN
SCL
VIN
KEYPAD OR
1µF
1µF
VDDIO
VDDIO
VDDIO
VDDIO
Figure 46. Alternate Schematic for Low Vf LEDs
D2
D1
D3
GND1
D2
D4
D3
GNDx
ADP8861
ADP8863
D4
D5
D5
D6
D6
GND2
D7
D7
D1
C1+
C1–
C2+
C2–
VOUT
NC
NC
NC
NC
C1+
C1–
C2+
C2–
1µF
VOUT
C1
1µF
C2
1µF