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PDF TSL2550 Data sheet ( Hoja de datos )
| Número de pieza | TSL2550 | |
| Descripción | AMBIENT LIGHT SENSOR | |
| Fabricantes | TAOS | |
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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
D Companding A/D for Wide Dynamic Range
D Rejects 50 Hz/60 Hz Lighting Ripple
D Two-Wire SMBus Serial Interface
D Single Supply Operation (2.7 V to 5.5 V)
D Low Active Power (1 mW typ)
D Power Down Mode
D Low-Profile Surface-Mount Packages
D RoHS Compliant
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.
VDD 1
NC 2
NC 3
GND 4
PACKAGE D
8-LEAD SOIC
(TOP VIEW)
8 SMBData
7 NC
6 NC
5 SMBCLK
PACKAGE T
4-LEAD SMD
(TOP VIEW)
VDD 1
4 SMBData
GND 2
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
VDD = 2.7 V to 5.5 V
Channel 0
Photodiode
Channel 1
Photodiode
Integrating
A/D Converter
Control Logic
Output Registers
Two-Wire Serial Interface
SMBCLK
SMBData
The
LUMENOLOGY
r
Company
Texas
Advarnced
Optoelectronic
Solutions
Inc.
1001 Klein Road S Suite 300 S Plano, TX 75074 S (972r) 673-0759
www.taosinc.com
Copyright E 2007, TAOS Inc.
1
1 page  
TSL2550
AMBIENT LIGHT SENSOR
WITH SMBus INTERFACE
TAOS029L − OCTOBER 2007
PARAMETER MEASUREMENT INFORMATION
SMBCLK
t(BUF)
SMBDATA
t(LOW)
t(R)
VIH
VIL
t(HDSTA)
t(HDDAT)
VIH
VIL
t(F)
t(HIGH) t(SUSTA)
t(SUDAT)
t(SUSTO)
P
Stop
Condition
S
Start
Condition
SMBCLK
S
Start
Stop
t(LOWSEXT)
SMBCLKACK
SMBCLKACK
t(LOWMEXT)
t(LOWMEXT)
t(LOWMEXT)
P
SMBDATA
Figure 1. SMBus Timing Diagrams
SMBCLK
1
91
9
SMBDATA
A6 A5 A4 A3 A2 A1 A0 R/W
D7 D6 D5 D4 D3 D2 D1 D0
Start by
Master
Frame 1 SMBus Slave Address Byte
ACK by
TSL2550
Frame 2 Command Byte
ACK by Stop by
TSL2550 Master
Figure 2. SMBus Timing Diagram for Send Byte Format
SMBCLK
1
91
9
SMBDATA
A6 A5 A4 A3 A2 A1 A0 R/W
D7 D6 D5 D4 D3 D2 D1 D0
Start by
Master
Frame 1 SMBus Slave Address Byte
ACK by
TSL2550
NACK by Stop by
Master Master
Frame 2 Data Byte From TSL2550
Figure 3. SMBus Timing Diagram for Receive Byte Format
The LUMENOLOGY r Company
r
www.taosinc.com
r
Copyright E 2007, TAOS Inc.
5
5 Page 
APPLICATION INFORMATION
TSL2550
AMBIENT LIGHT SENSOR
WITH SMBus INTERFACE
TAOS029L − OCTOBER 2007
The TSL2550 is intended for use in ambient light detection applications, such as display backlight control, where
adjustments are made to display brightness or contrast based on the brightness of the ambient light, as
perceived by the human eye. Conventional silicon detectors respond strongly to infrared light, which the human
eye does not see. This can lead to significant error when the infrared content of the ambient light is high, such
as with incandescent lighting, due to the difference between the silicon detector response and the brightness
perceived by the human eye.
This problem is overcome in the TSL2550 through the use of two photodiodes. One of the photodiodes
(channel 0) is sensitive to both 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 light on the
channel 0 digital output. The ADC digital outputs from the two channels are used in a formula to obtain a value
that approximates the human eye response in the commonly used Illuminance unit of Lux. For standard mode:
where:
Light Level (lux) + (Ch0 * Ch1) 0.39 e(*0.181R2 )
R = Ch1 Counts / (Ch0 Counts − Ch1 Counts)
The formula above was obtained by optical testing with fluorescent and incandescent light sources. The light
level calculated from the formula will be slightly higher than the actual light level for sunlight and will be slightly
lower than the actual light level for composite fluorescent and incandescent light sources.
NOTE:
Please see TAOS application notes for additional information, including implementing a display
brightness control system with the TSL2550, and for a simple implementation of the equation shown
above suitable for use in embedded microcontrollers.
Table 4 contains a summary of the typical sensor outputs for several common light sources.
LIGHT SOURCE
Fluorescent
Daylight (shade)
Incandescent
Table 4. Sensor Output Summary (Standard Mode)
ILLUMINANCE
(LUX)
297
201
42
CHANNEL 0
(COUNTS)
831
895
959
CHANNEL 1
(COUNTS)
68
343
671
RATIO:
CH1/CH0
0.082
0.383
0.7
LUX per CH0
COUNT
0.36
0.22
0.04
Light from 50 or 60 Hz sources, and especially fluorescent lighting, has a high harmonic content. Since the
TSL2550 integrates the ambient light over an approximately 400 millisecond interval (per channel), this light
ripple is typically reduced to less than ¼ LSB.
Power Supply Decoupling
The power supply lines must be decoupled with a 0.1 μF capacitor placed as close to the device package as
possible. The bypass capacitor should have low effective series resistance (ESR) and effective series
inductance (ESI), such as the common ceramic types, which provide a low impedance path to ground at high
frequencies to handle transient currents caused by internal logic switching.
The LUMENOLOGY r Company
r
www.taosinc.com
r
Copyright E 2007, TAOS Inc.
11
11 Page | ||
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| PDF Descargar | [ Datasheet TSL2550.PDF ] | |
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