LX1977 Datasheet PDF - Microsemi Corporation

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LX1977
Microsemi Corporation

Part Number LX1977
Description SMBus Ambient Light Sensor
Page 23 Pages


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LX1977
TM ® SMBus Ambient Light Sensor
PRODUCTION DATASHEET
DESCRIPTION
The LX1977 is a CMOS based Ambient
Light Sensor (ALS) with an I2C compatible
SMBus interface.
This device is ideal for controlling
display back lighting systems of low cost
consumer products such as TV, portable
computers, handheld devices, or medical
devices. The LX1977 is optimized for a
linear, accurate, and very repeatable input
and output transfer function. The device also
features adjustable input range and gain.
The LX1977 has a spectral response
that emulates the human eye. Specially
designed circuitry produces peak spectral
response at 555 nm, with IR response less
than 10% above 810 nm.
Input dynamic range of this device is
adjustable via SMBus command. It can be set
to either 0 ~ 500 lux, 0 ~ 1000 lux, 0 ~ 2500
lux or 0 ~ 5000 lux.
ALS internal compensation ensures
photodiode dark current are at very low
levels, providing high output accuracy at low
ambient light levels.
The LX1977 integrates a 12-bit Sigma-
Delta A/D converter that converts the ALS
photodiode output into a digital word. This
value is read via the I2C compatible SMBus
interface.
The LX1977 ALS is internally optimized
to an accuracy of approximately 5% over
temperature. The high accuracy and
repeatability of this device eliminates the
need of calibration during product
production, which results in reduced
assembly time and lower production cost.
The LX1977 is available in an 8-pin
MSOP package, and is operational over the
ambient temperature range -40˚C to 85˚C.
KEY FEATURES
ƒ Human Eye Spectral Response
ƒ Very Low IR Sensitivity
ƒ 12-bit Resolution
ƒ 5% Typical Accuracy
ƒ Rejection to 50/60Hz
Interference
ƒ Programmable Integration Time
ƒ Programmable Interrupt Pin
ƒ I2C compatible SMBus Interface
ƒ Easy Processor Interface
ƒ No Optical Filter Needed
APPLICATIONS
ƒ Backlight Control for Notebook
ƒ Backlight Control for TV
ƒ Handheld Devices
ƒ Medical Devices
Note: I2C is a trade mark of Philips
PACKAGE ORDER INFO
TA (°C) DU
3 x 5 Glass Top MSOP 8-pin
RoHS Compliant / Pb-free
-40 to 85
LX1977IDU
Note: Available in Tape & Reel. Append the letters “TR” to the part number.
(i.e. LX1977IDU -TR)
THERMAL DATA
θJA = 152 °C/W
THERMAL RESISTANCE-JUNCTION TO AMBIENT
Junction Temperature Calculation: TJ = TA + (PD x θJA).
The θJA numbers are guidelines for the thermal performance of the
device/pc-board system. All of the above assume no ambient airflow.
ABSOLUTE MAXIMUM RATINGS
VDD ............................................................................................................... -0.3 to 6V DC
Input Voltage to All Input Pins ........................................................... -0.3V to VDD + 0.3V
SMBus Pin Voltage (SCL, SDA) .................................................................. -0.3V to 5.5V
SMBus Pin Current (SCL, SDA) ........................................................................... < 10 mA
Operating Temperature Range ........................................................................ -40 to +85°C
Storage Temperature Range.............................................................................-40 to 100°C
RoHS / Pb-free Peak Package Solder Reflow Temperature
(40 seconds maximum exposure).................................................................... 260° (+0, -5)
PACKAGE PIN OUT
Notes: Exceeding these ratings could cause damage to the device. All voltages are with respect to
Ground. Currents are positive into, negative out of specified terminal.
GLASS TOP MSOP 8 PIN
(Top View)
RoHS / Pb-free 100% Matte Tin
Copyright © 2010
Rev. 1.0, 2010-03-25
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1



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TM
VDD
RSET
VDD
RSET
SDA
LX1P9a7r7t SCL
ADR VSS INT
LX1977
® SMBus Ambient Light Sensor
PRODUCTION DATASHEET
PRODUCT HIGHLIGHT
VDD
LX1977 DCOUNT vs LUX @ Fosc=40.96kHz, TINT=100mS
4000 Vcc = 3.3V
µP
VSS
3000
2000
1000
0
0
0 ~ 500 lux
0 ~ 1000 lux
0 ~ 5000 lux
0 ~ 2500 lux
1000
2000
3000
LUX INPUT
4000
5000
6000
SIMPLIFIED BLOCK DIAGRAM
VDD
Pre
Amplifier
Sigma-
Delta
ADC
SMBus
Interface
Figure 1 – Simplified Block Diagram
VDD
SDA
SCL
INT
ADR
VSS
RSET
PACKAGE PHOTO
Figure 2 – Product Photo
Name
VDD
SDA
SCL
INT
ADR
RSET
NC
VSS
Pin #
1
2
3
4
5
6
7
8
Dir
PWR
I/O
I
O
I
I
PWR
FUNCTIONAL PIN DESCRIPTION
Description
Power Supply Voltage
SMBus Data – Connect To SMBus Data Line
SMBus Clock – Connect To SMBus Clock Line
Interrupt Output Pin, Active Low, Open Drain
SMBus Address – The Address For This Device Is Determined By The State Of This Pin.
ADR = GND sets address 20H, ADR = OPEN sets address 22H, ADR=VDD sets address 70H.
Gain Setting. For Gain Fine Adjustment. Typically, connect this pin to ground through a 1% 267k
resistor.
No Connection Pin
Ground Reference For Power And Signal Output
Copyright © 2010
Rev. 1.0, 2010-03-25
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2



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LX1977
TM ® SMBus Ambient Light Sensor
PRODUCTION DATASHEET
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature 0°C TA 70°C and the
following test conditions: 3.0V VDD 4.5V
Parameter
Symbol
Test Conditions / Comment
Min Typ Max Units
POWER SUPPLY
Operational Voltage
Supply Current
Supply Current
VDD Note 5
IDD
IDD Shut Down ALS
3.0 4.5 V
0.2 mA
15 µA
INTERNAL
Internal Oscillator Frequency
FOSC
3.0V VDD.3.6V
3.0V VDD.4.5V
38.91
36.86
40.96 43.00
40.96 45.06
kHz
ALS RESPONSE
Peak Spectral Response
Infrared Response
Full Scale ADC Output Value
@ FOSC= 40.96kHz,
RANGE_SEL = 00b (0 ~ 500 lux)
RANGE_SEL = 01b (0 ~ 1000 lux)
RANGE_SEL = 10b (0 ~ 5000 lux)
RANGE_SEL = 11b (0 ~ 2500 lux)
Enable Time
Disable Time
Dynamic Response Time
λPR(ALS)
ΔIR
DCOUNT
DCOUNT
DCOUNT
DCOUNT
tON
tOFF
TF(90%~10%)
TR(10%~90%)
EV(white) = 100 lux, EV(810nm) = 14.6µW/cm2,
Note 3
TINT = 100 ms, Note 4
TINT = 50 ms, Note 4
TINT = 25 ms, Note 4
TINT = 6.25 ms, Note 4
Software Enable
Software Disable
Light Input Change From 200 lux to 20 lux
Light Input Change From 20 lux to 200 lux
555 nm
-8 8 %
4095
2047
1023
Counts
255
100 µs
100 µs
1
ms
1
ADC
Non-Linearity
ALS
ADC Output Count
@ FOSC = 40.96kHz, TINT = 50ms
RANGE_SEL = 01b (0 ~ 1000 lux)
DNL
DCOUNT
TINT = 100ms, RANGE_SEL=00b
Note 6
EV = 200 lux, Note 1,2
EV = 500 lux, Note 1,2
EV = 1000 lux, Note 1,2
-5 5 %
346
880
1768
372
931
1861
398
982
1955
Counts
ADC Output Count
@ FOSC = 40.96kHz, TINT = 100ms
RANGE_SEL = 00b (0 ~ 500 lux)
ADC Output Count
@ FOSC = 40.96kHz, TINT = 100ms
RANGE_SEL = 01b (0 ~ 1000 lux)
ADC Output Count
@ FOSC = 40.96kHz, TINT = 100ms
RANGE_SEL = 10b (0 ~ 5000 lux)
ADC Output Count
@ FOSC = 40.96kHz, TINT = 100ms
RANGE_SEL = 11b (0 ~ 2500 lux)
Dark ADC Count Value
DCOUNT
DCOUNT
DCOUNT
DCOUNT
DCOUNT
EV = 100 lux, Note 1,2
EV = 200 lux, Note 1,2
EV = 500 lux, Note 1,2
EV = 200 lux
EV = 500 lux
EV = 1000 lux
EV = 500 lux
EV = 1000 lux
EV = 2000 lux
EV = 500 lux
EV = 1000 lux
EV = 2000 lux
EV = 0 lux, TA = 25°C, RANGE_SEL=00b,
TINT=100mS
692
1403
3537
745
1489
3723
733
1808
3535
364
713
1437
734
1433
2851
0
797
1575
3909
Counts
Counts
Counts
Counts
4 Counts
Copyright © 2010
Rev. 1.0, 2010-03-25
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3



No Preview Available !

LX1977
TM ® SMBus Ambient Light Sensor
PRODUCTION DATASHEET
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, the following specifications apply over the operating ambient temperature 0°C TA 70°C and the
following test conditions: 3.0V VDD 4.5V
Parameter
SMBUS INTERFACE
Symbol
Test Conditions / Comment
EV = 0 lux, TA = 70°C, RANGE_SEL=00b,
TINT=100mS, Note 7
Min Typ Max Units
18
Clock Frequency
High Level Input Voltage
Low Level Input Voltage
FCLK
VSDA
VSCL
10 400 kHz
0.8 V
2.1 V
Input Leakage Current
SDA Low Output Voltage
ISDA/ISCL
VSDA
ISDA = 3mA
-5 5 µA
0.4 V
SDA Current Sinking Capacity
ISDA
3 mA
INT Low Output Voltage
INT Leakage Current
VINT
ILEAK
IINT = 3mA
0.4 V
-10 10 µA
ADR High Level Input Voltage
ADR Open
ADR Low Level Input Voltage
VADR
80%
40%
60%
20%
VDD
VDD
VDD
ADR Input Leakage Current
IADR
-10 10 µA
Notes:
1. In production, the input irradiance is supplied from a point source which is a white LED.
2. See Figure 3
3.
ΔIR
=
D (ECOUNT V(WHITE) + EV(IR)) DCOUNT(EV(WHITE))
DCOUNT(EV(WHITE))
4. Guarantee by scan tests.
5. Specifications in the EC table are for 3.0V ~ 4.5V. Device is operational down to 2.5V and up to 5.0V with relaxed specifications.
6. Gain1 = (DCOUNT2-DCOUNT1) / (Lux2-Lux1), Gain2 = (DCOUNT3-DCOUNT2) / (Lux3-Lux2), DNL1 = (Gain1 * 2 / (Gain1+Gain2) -1) %, DNL2 = (Gain2 *
2 / (Gain1+Gain2) – 1) %. Lux1 = 100 lux, Lux2 = 200 lux, Lux3 = 500 lux.
7. For the setting RANGE_SEL=00b and TINT=100mS, the full scale output is typical 3723 decimal. A dark ADC output count of maximum 18 at
TA = 70°C is only 0.5% of 3723.
White
LED
TEST CIRCUITS
VDD
810nm
RSET
VDD
SDA
LX1P9a7r7t SCL
ADR VSS INT
To Test
Computer
Figure 3 – ALS Output Measurement
Copyright © 2010
Rev. 1.0, 2010-03-25
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4



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