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TSL2550
AMBIENT LIGHT SENSOR
WITH SMBus INTERFACE
TAOS029L
−
OCTOBER 2007
D
Converts Light Intensity to Digital Signal
D
Infrared Compensation to Approximate
Human Eye Response
PACKAGE D
8-LEAD SOIC
(TOP VIEW)
D
D
D
D
D
D
D
D
Companding A/D for Wide Dynamic Range
Rejects 50 Hz/60 Hz Lighting Ripple
Two-Wire SMBus Serial Interface
Single Supply Operation (2.7 V to 5.5 V)
Low Active Power (1 mW typ)
Power Down Mode
Low-Profile Surface-Mount Packages
RoHS Compliant
V
DD
1
NC 2
NC 3
GND 4
8 SMBData
7 NC
6 NC
5 SMBCLK
PACKAGE T
4-LEAD SMD
(TOP VIEW)
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.
V
DD
1
GND 2
4 SMBData
3 SMBCLK
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
Channel 0
Photodiode
Channel 1
Photodiode
V
DD
= 2.7 V to 5.5 V
Integrating
A/D Converter
Control Logic
Output Registers
SMBCLK
SMBData
Two-Wire Serial Interface
The
LUMENOLOGY
r
Company
Texas Advanced Optoelectronic Solutions Inc.
1001 Klein Road
S
Suite 300
S
Plano, TX 75074
S
(972) 673-0759
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www.taosinc.com
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Copyright
E
2007, TAOS Inc.
TAOS [ TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS ]
