ANALOG DEVICES ADP8870 Service Manual

Charge-Pump, Parallel Backlight Driver

V

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

with Image Content PWM Input

ADP8870

APPLICATIONS

Mobile display backlighting
Mobile phone keypad backlighting
RGB LED lighting
LED indication
General backlighting of small format displays

TYPICAL OPERATING CIRCUIT

OPTIONAL

V

PHOTOSENSOR

OUT

DD_ALS

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

V

IN

1µF

VDDIO

D1 D2 D3 D4 D5 D6 D7 CMP_IN

Fading override

2

I

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

= 2.5 V, with undervoltage lockout

IN

(UVLO) at 2.0 V.

nRST

SDA

SCL

nINT

PWM

ADP8870

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

Figure 1.

lead frame chip scale package (LFCSP)

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 photo­transistor. 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

For more information about the ADP8870, including the complete data sheet, contact your local Analog Devices, Inc., sales office at

www.analog.com/sales.

Rev. Sp0

Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.

60 mA (maximum). All LEDs are individually programmable for
minimum/maximum current and fade-in/fade-out times through

2

an I

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

of 240 mA from a supply of 2.5 V to 5.5 V. A full

OUT

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.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] ©2010 Analog Devices, Inc. All rights reserved.

PHOTO­SENSOR

0.1µF

0.1µF

1µF

C1+

C1–

C2+

C2–

GND

V

OUT

C1
1µF

C2
1µF

08829-001

ADP8870

OUTLINE DIMENSIONS

2.190

2.150

2.110

4

1

23

BALL 1

IDENTIFIER

0.645

0.600

0.555

SEATING

PLANE

INDICATOR

SEATING

PIN 1

0.80

0.75

0.70

PLANE

2.395

TOP VIEW

(BALL SIDE DOWN)

SIDE VIEW

0.287

0.267

0.247

2.355

2.315

0.415

0.400

0.385

1.60 REF

0.40
REF

COPLANARITY

0.05

0.230

0.200

0.170

Figure 2. 20-Ball Wafer Level Chip Scale Package [WLCSP]

(CB-20-7)

Dimensions shown in millimeters

4.10

4.00 SQ

3.90

0.50

BSC

0.50

0.40

0.30

0.05 MAX

0.02 NOM

0.20 REF

COPLANARITY

0.08

0.30

0.25

0.20

16

15

11

10

BOTTOM VIEWTOP VIEW

BOTTOM VIEW

(BALL SIDE UP)

1.20 REF

N

1

P

I

D

C

I

A

N

I

20

EXPOSED

1

PAD

5

6

FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
SECTION OF THIS DATA SHEET.

2.65

2.50 SQ

2.35

0.25 MIN

A

B

C

D

E

110609-A

R

O

T

COMPLIANTTOJEDEC STANDARDS MO-220-WGGD.

Figure 3. 20-Lead Lead Frame Chip Scale Package [LFCSP_WQ]

4 mm × 4 mm Body, Very Very Thin Quad

Figure 4. Tape and Reel Orientation for WLCSP Units

©2010 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D08829F-0-6/10(Sp0)

08829-031

Dimensions shown in millimeters

(CP-20-10)

Rev. Sp0 | Page 2 of 2

061609-B

Figure 5. Tape and Reel Orientation for LFCSP Units

08829-032