Datasheet

Data Sheet ADP8866
Rev. A | Page 11 of 52
THEORY OF OPERATION
The ADP8866 combines a programmable backlight LED charge
pump driver with automatic blinking functions. Nine LED drivers
can be independently programmed at currents up to 25 mA.
The current level, fade time, and blinking rate can be programmed
once and executed autonomously on a loop. Separate fade-in
and fade-out times can be set for the backlight LEDs.
Driving all of this is a two capacitor charge pump with gains of
1×, 1.5×, and 2×. This setup is capable of driving a maximum
I
OUT
of 240 mA from a supply of 2.5 V to 5.5 V. A full suite of
safety features including short-circuit, overvoltage, and over-
temperature protection allows easy implementation of a safe
and robust design. Additionally, input inrush currents are
limited via an integrated soft start combined with controlled
input to output isolation.
09478-028
C1
1µF
C2
1µF
nINT
C
OUT
VOUT
C
IN
VIN
V
REFS
I
REFS
STANDBY
EN
VIN
C1+
SDA
SCL
I
2
C LOGIC
STANDBY
ILED CONTROL
C1–
C2+
C2–
nRST
NOISE FILTER
50µs
RESET
D2 D3
D4 D5
D6 D7
D1
ID1
ID2
ID3
ID4 ID5
ID6
ID7
GAIN
SELECT
LOGIC
CHARGE
PUMP
LOGIC
GND
CLK
UVLO
CHARGE
PUMP
(1x, 1.5x, 2x)
SOFT
START
LED
OUTPUT
CURRENT
ID1
ID2
ID3
ID4
ID5
ID6
ID7
I
SS
D8 D9
ID8 ID9
ID8
ID9
nINT MUX INT
PWM
VIN
GAIN CONTROL
Figure 27. Detailed Block Diagram