Datasheet

Charge-Pump, Parallel Backlight Driver
with Image Content PWM Input
ADP8870
Rev. Sp0
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FEATURES
Charge pump with automatic gain selection of 1×, 1.5×, and
2× for maximum efficiency
Two high accuracy (±5%) phototransistor inputs for
automated ambient light sensing (ALS)
5 programmable ambient light-sensing zones for optimal
backlight power savings
Independent ALS control of D7, for automated response of
keypad lighting to ambient light levels
PWM input can be used for content adaptive brightness
control (CABC) of any, or all, of the LEDs
PWM input scales the LED output current
7 independent, programmable LED drivers
6 drivers capable of 30 mA (maximum)
1 driver capable of 60 mA (maximum)
Programmable maximum current limit (128 levels)
Standby mode for <1 μA current consumption
16 programmable fade-in and fade-out times (0.1 sec to 5.5 sec)
with choice of square or cubic rates
Fading override
I
2
C-compatible interface for all programming
Dedicated reset pin and built-in power-on reset (POR)
Short-circuit, overvoltage, and overtemperature protection
Internal soft start to limit inrush currents
Input-to-output isolation during faults or shutdown
Operates down to V
IN
= 2.5 V, with undervoltage lockout
(UVLO) at 2.0 V.
Available in a small, 2.15 mm × 2.36 mm × 0.6 mm wafer level
chip scale package (WLCSP) or a 4 mm × 4 mm × 0.75 mm
lead frame chip scale package (LFCSP)
APPLICATIONS
Mobile display backlighting
Mobile phone keypad backlighting
RGB LED lighting
LED indication
General backlighting of small format displays
TYPICAL OPERATING CIRCUIT
08829-001
D1 D2 D3 D4 D5 D6 D7 CMP_IN
V
OUT
OPTIONAL
PHOTOSENSOR
PHOTO-
SENSOR
V
DD_ALS
0.1µF
0.1µF
V
IN
1µF
GND
C2+
C2–
C2
1µF
C1+
C1–
C1
1µF
V
OUT
1µF
ADP8870
nINT
PWM
SDA
SCL
VDDIO
nRST
Figure 1.
GENERAL DESCRIPTION
The ADP8870 combines a programmable backlight LED
charge-pump driver with automatic phototransistor control of
the brightness (LED current) and a PWM input to control the
scale of the output current. This combination allows significant
power savings because it automatically changes the current
intensity based on the sensed ambient lighting levels and the
display image content. It performs this function automatically,
eliminating the need for a processor to monitor the photo-
transistor. The light intensity thresholds are fully programmable
via the I
2
C interface.
The ADP8870 allows up to six LEDs to be independently driven up
to 30 mA (maximum). An additional seventh LED can be driven to
60 mA (maximum). All LEDs are individually programmable for
minimum/maximum current and fade-in/fade-out times through
an I
2
C interface. These LEDs can also be combined into groups
to reduce the processor instructions during fade-in and fade-out.
Driving these components 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
overtemperature 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.
For more information about the ADP8870, including the complete data sheet, contact your local Analog Devices, Inc., sales office at
www.analog.com/sales.