TSL2550
AMBIENT LIGHT SENSOR
WITH SMBus INTERFACE
TAOS029 - APRIL 2003
1
The
LUMENOLOGY
r
Company
t
t
Copyright
E
2003, TAOS Inc.
www.taosinc.com
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 Package
Description
The TSL2550 is a digital 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.
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
V
DD
= 2.7 V to 5.5 V
Channel 0
Photodiode
Channel 1
Photodiode
t
t
Texas Advanced Optoelectronic Solutions Inc.
800 Jupiter Road, Suite 205
S
Plano, TX 75074
S
(972) 673-0759
8 SMBData
7 NC
6 NC
5 SMBCLK
PACKAGE D
8-LEAD SOIC
(TOP VIEW)
V
DD
1
NC 2
NC 3
GND 4
PACKAGE T
4-LEAD SMD
(TOP VIEW)
V
DD
1
GND 2
4 SMBData
3 SMBCLK
TSL2550
AMBIENT LIGHT SENSOR
WITH SMBus INTERFACE
TAOS029 - APRIL 2003
2
t
t
Copyright
E
2003, TAOS Inc.
The
LUMENOLOGY
r
Company
www.taosinc.com
Terminal Functions
TERMINAL
NAME
D PKG
NO.
T PKG
NO.
TYPE
DESCRIPTION
GND
4
2
Power supply ground. All voltages are referenced to GND.
SMBCLK
5
3
I
SMBus serial clock input terminal -- clock signal for SMBus serial data.
SMBData
8
4
I/O
SMBus serial data I/O terminal -- serial data I/O for SMBus.
V
DD
1
1
Supply voltage.
Available Options
DEVICE
T
A
PACKAGE - LEADS
PACKAGE DESIGNATOR
ORDERING NUMBER
TSL2550
- 25
C to 85
SOIC-8
D
TSL2550D
TSL2550
- 25
C to 85
T-4
T
TSL2550T
Absolute Maximum Ratings over operating free-air temperature range (unless otherwise noted)
Supply voltage, V
DD
(see Note 1)
6 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Digital output voltage range, V
O
-0.3 V to +6 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Digital output current, I
O
10 mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SMBus input/output current, I
(SMBIN)
-1 mA to 20 mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating free-air temperature range, T
A
-25
C to 85
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Storage temperature range, T
stg
- 25
C to 85
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ESD tolerance, human body model
2000 V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTE 1: All voltages are with respect to GND.
Recommended Operating Conditions
MIN
MAX
UNIT
Supply voltage, V
DD
2.7
5.5
V
Operating free-air temperature, T
A
0
70
C
SMBus input low voltage @ V
DD
= 3.3 V
5%, V
IL
0.8
V
SMBus input high voltage @ V
DD
= 3.3 V
5%, V
IH
2.1
V
SMBus operating frequency, f
(SMBCLK)
10
100
kHz
TSL2550
AMBIENT LIGHT SENSOR
WITH SMBus INTERFACE
TAOS029 - APRIL 2003
3
The
LUMENOLOGY
r
Company
t
t
Copyright
E
2003, TAOS Inc.
www.taosinc.com
Electrical Characteristics over recommended operating free-air temperature range (unless
otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
V
SMBus output low voltage
I
O
= 50
A
0.01
V
V
OL
SMBus output low voltage
I
O
= 4 mA
0.4
V
I
Supply current
Active, VSMBCLK and VSMDATA = V
DD,
V
DD
= 3.3 V
5%
0.35
0.6
mA
I
DD
Supply current
Power down, VSMBCLK and VSMDATA =
V
DD,
V
DD
= 3.3 V
5%
10
A
I
IH
High level input current
VI = V
DD
5
A
I
IL
Low level input current
VI = 0
-5
A
Operating Characteristics, V
DD
= 3.3 V, T
A
= 25
5
C (unless otherwise noted) (see Notes 2, 3, 4)
PARAMETER
TEST CONDITIONS
CHANNEL
MIN
TYP
MAX
UNIT
E
0
Ch0
1
E
e
= 0
Ch1
1
ADC count value
p
= 640 nm
Ch0
639
799
959
counts
ADC count value
p
= 640 nm
E
e
= 77
W/cm
2
Ch1
85
counts
p
= 940 nm
Ch0
511
799
1039
p
= 940 nm
E
e
= 150
W/cm
2
Ch1
703
ADC count value ratio: Ch1/Ch0
p
= 640 nm, E
e
= 77
W/cm
2
0.070
0.106
0.175
ADC count value ratio: Ch1/Ch0
p
= 940 nm, E
e
= 150
W/cm
2
0.70
0.88
1.20
p
= 640 nm
Ch0
10.4
R
Irradiance responsivity
p
= 640 nm
E
e
= 77
W/cm
2
Ch1
1.1
counts/
(
W/
R
e
Irradiance responsivity
p
= 940 nm
Ch0
5.3
(
W/
cm
2
)
p
= 940 nm
E
e
= 150
W/cm
2
Ch1
4.7
cm
2
)
Fluorescent light source: 300 Lux
Ch0
2.8
R
Illuminance responsivity
Fluorescent light source: 300 Lux
Ch1
0.23
counts/
R
v
Illuminance responsivity
Incandescent light source: 50 Lux
Ch0
19
counts/
lux
Incandescent light source: 50 Lux
Ch1
13
(Sensor Lux) / (actual Lux) (Note 5)
Fluorescent light source: 300 Lux
0.65
1
1.35
(Sensor Lux) / (actual Lux) (Note 5)
Incandescent light source: 50 Lux
0.5
1
1.5
NOTES: 2. Optical measurements are made using small-angle incident radiation from light-emitting diode optical sources. Visible 640 nm LEDs
and infrared 940 nm LEDs are used for final product testing for compatibility with high volume production.
3. The 640 nm irradiance E
e
is supplied by an Al
I
nGaP light-emitting diode with the following characteristics: peak wavelength
p = 640 nm and spectral halfwidth
= 17 nm.
4. The 940 nm irradiance E
e
is supplied by a GaAs light-emitting diode with the following characteristics: peak wavelength
p = 940 nm and spectral halfwidth
= 40 nm.
5. The sensor Lux is calculated using the empirical formula shown on p. 12 of this data sheet based on measured Ch0 and Ch1 ADC
count values for the light source specified. Actual Lux is obtained with a commercial luxmeter. The range of the (sensor Lux) / (actual
Lux) ratio is estimated based on the variation of the 640 nm and 940 nm optical parameters. Devices are not 100% tested with
fluorescent or incandescent light sources.
TSL2550
AMBIENT LIGHT SENSOR
WITH SMBus INTERFACE
TAOS029 - APRIL 2003
4
t
t
Copyright
E
2003, TAOS Inc.
The
LUMENOLOGY
r
Company
www.taosinc.com
AC Electrical Characteristics, V
DD
= 3.3 V, T
A
= 25
5
C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
t
(CONV)
Conversion time, per channel
400
ms
f
(SMBCLK)
Clock frequency
100
kHz
t
(BUF)
Bus free time between start and stop condition
4.7
s
t
(HDSTA)
Hold time after (repeated) start condition. After
this period, the first clock is generated.
4
s
t
(SUSTA)
Repeated start condition setup time
4.7
s
t
(SUSTO)
Stop condition setup time
4
s
t
(HDDAT)
Data hold time
300
ns
t
(SUDAT)
Data setup time
250
ns
t
(LOW)
SMBCLK clock low period
4.7
s
t
(HIGH)
SMBCLK clock high period
4
s
t
(TIMEOUT)
Detect clock/data low timeout
25
35
ms
t
F
Clock/data fall time
300
ns
t
R
Clock/data rise time
1000
ns
C
i
Input pin capacitance
10
pF
TSL2550
AMBIENT LIGHT SENSOR
WITH SMBus INTERFACE
TAOS029 - APRIL 2003
5
The
LUMENOLOGY
r
Company
t
t
Copyright
E
2003, TAOS Inc.
www.taosinc.com
PARAMETER MEASUREMENT INFORMATION
SMBDATA
SMBCLK
Stop
Start
SMBCLK
ACK
t
(LOWMEXT)
t
(LOWMEXT)
t
(LOWSEXT)
SMBCLK
ACK
t
(LOWMEXT)
Start
Condition
Stop
Condition
P
SMBDATA
t
(SUSTO)
t
(SUDAT)
t
(HDDAT)
t
(BUF)
V
IH
V
IL
SMBCLK
t
(SUSTA)
t
(HIGH)
t
(F)
t
(R)
t
(HDSTA)
t
(LOW)
V
IH
V
IL
P
S
S
Figure 1. SMBus Timing Diagrams
A0
A1
A2
A3
A4
A5
A6
SMBCLK
Start by
Master
SMBDATA
1
9
1
9
D1
D2
D3
D4
D5
D6
D7
D0
R/W
Frame 1 SMBus Slave Address Byte
Frame 2 Command Byte
ACK by
TSL2550
Stop by
Master
ACK by
TSL2550
Figure 2. SMBus Timing Diagram for Send Byte Format
A0
A1
A2
A3
A4
A5
A6
SMBCLK
Start by
Master
SMBDATA
1
9
1
9
D1
D2
D3
D4
D5
D6
D7
D0
R/W
Frame 1 SMBus Slave Address Byte
Frame 2 Data Byte From TSL2550
ACK by
TSL2550
Stop by
Master
NACK by
Master
Figure 3. SMBus Timing Diagram for Receive Byte Format
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