TSL2550

AMBIENT LIGHT SENSOR

WITH SMBus INTERFACE

TAOS029L − OCTOBER 2007

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The LUMENOLOGY r Company

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Copyright E 2007, TAOS Inc.

www.taosinc.com

Human Eye Response

Description

The TSL2550 is a digital-output light sensor with

a two-wire, SMBus serial interface. It combines

two photodiodes and a companding analog-to-

digital converter (ADC) on a single CMOS

integrated circuit to provide light measurements

over an effective 12-bit dynamic range with a

response similar to that of the human eye.

The TSL2550 is designed for use with broad wavelength light sources. One of the photodiodes (channel 0) is

sensitive to visible and infrared light, while the second photodiode (channel 1) is sensitive primarily to infrared

light. An integrating ADC converts the photodiode currents to channel 0 and channel 1 digital outputs. Channel

1 digital output is used to compensate for the effect of the infrared component of ambient light on channel 0

digital output. The ADC digital outputs of the two channels are used to obtain a value that approximates the

human eye response in the commonly used unit of Lux.

This device is intended primarily for use in applications in which measurement of ambient light is used to control

display backlighting such as laptop computers, PDAs, camcorders, and GPS systems. Other applications

include contrast control in LED signs and displays, camera exposure control, lighting controls, etc. The

integrating conversion technique used by the TSL2550 effectively eliminates the effect of flicker from

AC-powered lamps, increasing the stability of the measurement.

Functional Block Diagram

SMBCLK

Two-Wire Serial Interface

Integrating

A/D Converter

Control Logic

Output Registers

SMBData

Channel 0

Photodiode

Channel 1

Photodiode

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Texas Advanced Optoelectronic Solutions Inc.

1001 Klein Road S Suite 300 S Plano, TX 75074 S (972) 673-0759

8 SMBData

7 NC

6 NC

5 SMBCLK

PACKAGE D

8-LEAD SOIC

(TOP VIEW)

NC 2

NC 3

GND 4

PACKAGE T

4-LEAD SMD

(TOP VIEW)

GND 2

4 SMBData

3 SMBCLK