LX1973A
TM
®
Automotive Light Sensor
P
RODUCTION
D
ATA
S
HEET
DESCRIPTION
KEY FEATURES
Nearly Perfect
Best Eye™
Human Eye Spectral Response
25C Dark Current <0.005 lux
5 Decades Compressed Output
10% Accuracy Over
Temperature
Scalable Output Voltage
No Optical Filters Needed
The LX1973A is a wide dynamic
range light sensor with a very low
dark current that is optimized for
sensing low level light signals that
typically occur under dark or
darkening outdoor ambient lighting.
The LX1973A has been optimized for
automotive systems such as headlamp
brightness control or rear view mirror
contrast control. Its radical (fractional
exponent) response when interfaced
with an 8 bit DAC can detect levels
down to 0.001 lux or levels as high as
500 lux.
The spectral response of the
integrated light sensor closely
emulates the human eye so it ignores
light such as infrared which emits
energy but doesn’t aid vision. This
eliminates the need for an Infrared
filter required with competitor’s light
sensors.
The LX1973A internal circuitry
consists of a diode array with
Microsemi’s
Best Eye™
processing that
provides a nearly perfect photopic light
wavelength response curve. The sensor
output feeds into a wide dynamic range
compression amplifier that provides
accurate resolution over five decades of
ambient light. The integrated dark
current cancellation circuit facilitates
accurate sensing of light below 0.01
lux. The current source output of the
LX1973A can be gain scaled using one
external resistor.
The LX1973A is internally trimmed
to an initial accuracy of 5% at room
temperature and a light level of 10lux.
Accuracy of 10% is maintained over the
full temperature range (-40 to +85°C).
WWW .
Microsemi
.C
OM
APPLICATIONS
Auto headlamp control
Auto mirror contrast control
IMPORTANT:
For the most current data, consult
MICROSEMI’s
website:
http://www.microsemi.com
Protected By US Patents: 6,787,757; Patents Pending
PRODUCT HIGHLIGHT
LX1973A Response
5V
Output (in Volts)
4.0
3.0
2.0
1.0
0.0
0.001
LX1973A
Part
V
OUT
R
LOAD
0.01
0.1
1
10
100
Ambient Light (in lux)
LX1973A
LX1973A
PACKAGE ORDER INFO
T
A
(°C)
-40 to 85
DR
Plastic MSOP Reversed Form
8-Pin
RoHS Compliant / Pb-free
DU
Plastic MSOP
8-pin
LX1973AIDU
RoHS Compliant / Pb-free
LX1973AIDR
Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX1973AIDU-TR)
Copyright
©
2005
Rev. 1.2, 2009-05-26
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
LX1973A
TM
®
Automotive Light Sensor
P
RODUCTION
D
ATA
S
HEET
ABSOLUTE MAXIMUM RATINGS
V
DD
................................................................................................................. -0.3 to 6 V
DC
SNK/SRC (Output Compliance Voltage)........................................... -0.3 to V
DD
+ 0.3V
DC
SNK/SRC (Maximum Output Current)................................................... Internally Limited
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)
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.
V
DD
BP
NC
OUT
PACKAGE PIN OUT
V
SS
BP
NC
NC
WWW .
Microsemi
.C
OM
DU P
ACKAGES
(Top View)
YWWA
THERMAL DATA
DR
Plastic MSOP 8-Pin Reverse Form
39°C/W
206°C/W
V
SS
BP
NC
NC
V
DD
BP
NC
OUT
973A
THERMAL RESISTANCE
-
JUNCTION TO
C
ASE
,
θ
JC
P
ACKAGE
M
ARKING
(Bottom View)
THERMAL RESISTANCE
-
JUNCTION TO
A
MBIENT
,
θ
JA
YWWA
DU
Plastic MSOP 8-Pin
39°C/W
206°C/W
THERMAL RESISTANCE
-
JUNCTION TO
C
ASE
,
θ
JC
THERMAL RESISTANCE
-
JUNCTION TO
A
MBIENT
,
θ
JA
V
SS
BP
NC
NC
V
DD
BP
NC
OUT
973A
Junction Temperature Calculation: T
J
= T
A
+ (P
D
x
θ
JA
).
The
θ
JA
numbers are guidelines for the thermal performance of the device/pc-board system. All of the
above assume no ambient airflow.
P
ACKAGE
M
ARKING
(Top View)
FUNCTIONAL PIN DESCRIPTION
Name
V
DD
V
SS
OUT
BP
NC
Power Supply Voltage
Ground Reference for Power and Signal Output
Current Output
Internally Connected to Bonding Pad. This Pin Can Be Left Open or
Connected to V
SS
No Connection Pin
SIMPLIFIED BLOCK DIAGRAM
Description
V
DD
BP
NC
OUT
V
SS
BP
NC
NC
DR P
ACKAGES
(Bottom View)
RoHS / Pb-free NiPdAu Finish
MSL 2/260°C/1 Year
V
DD
P
ACKAGE
D
ATA
P
ACKAGE
D
ATA
Photopic
Sensor with
Dark Current
Cancellation
Pre
Amplifier
Com-
pression
Amplifier
OUT
V
SS
Figure 1 –
Simplified Block Diagram
Copyright
©
2005
Rev. 1.2, 2009-05-26
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
LX1973A
TM
®
Automotive Light Sensor
P
RODUCTION
D
ATA
S
HEET
Unless otherwise specified, the following specifications apply over the operating ambient temperature -40°C
≤
T
A
otherwise noted and the following test conditions: See Note 1, V
DD
=5V.
Parameter
Operational Voltage
Supply Current
Power Supply Rejection Ratio
Peak Spectral Response
Infrared Response
Light to Current Gain
Saturation Current
Radiant Sensitive Area
Flat Top Package (note 5)
Output Current
Output Current
Output Current
Output Current
Dark Current (equivalent lux)
Symbol
V
DD
I
DD
PSRR
λ
PR
Test Conditions
EV = 1.0 lux
V
RIPPLE
= 100mV
P-P
, f = 10kHz; C
OUT
= 0.1µF
E
V(white)
= 100 lux, E
V(810nm)
= 14.6µW/cm
2
,
Note 3
See application section for equation
570
ELECTRICAL CHARACTERISTICS
≤
85°C except where
WWW .
Microsemi
.C
OM
LX1973A
Min
Typ
Max
4.5
5.5
0.2
0.25
30
35
580
-5
1
5
Units
V
mA
dB
nm
%
µA
mm
2
I
DD
(
λ
)
I
DD
(
λ
PR
)
G
L
I
SAT
I
OUT(0.01)
I
OUT(1.0)
I
OUT(10)
I
OUT(100)
I
OUT (DARK)
0.20
E
V
= 0.01 lux @ 25°C, Note 1,2
E
V
= 1.0 lux, Note 1,2
E
V
= 10 lux, Note 1,2
E
V
= 100 lux, Note 1,2
E
V
= 0 lux, T
A
= 20°C, Note 4
E
V
= 0 lux, T
A
= 50°C, Note 4
1.0 lux to 0.01 lux
0.01 lux to 1.0 lux
E
V
= 0.01 lux @ 25°C, Note 1,2
E
V
= 1.0 lux, Note 1,2
E
V
= 10 lux, Note 1,2,
E
V
= 100 lux, Note 1,2
E
V
= 0 lux, T
A
= 20°C, Note 4
E
V
= 0 lux, T
A
= 50°C, Note 4
1.0 lux to 0.01 lux
0.01 lux to 1.0 lux
32
103
183
320
36
114
203
360
450
2100
1.5
0.2
36
117
208
370
450
2100
1.5
0.2
40
125
223
400
900
5000
3
0.5
40
128
229
407
900
5000
3
0.5
µA
µA
µA
µLux
sec
sec
µA
µA
µA
µLux
sec
sec
Dynamic Response Time
T
DR
(to 10% settling error point)
Reverse Form Package (note 6)
Output Current
I
OUT(0.01)
Output Current
I
OUT(1.0)
Output Current
I
OUT(10)
Output Current
I
OUT(100)
Dark Current (equivalent lux)
Dynamic Response Time
(to 10% settling error point)
I
OUT (DARK)
T
DR
32
105
187
333
Notes:
1. The input irradiance is supplied from a point source which is a white light emitting diode (LED); Fairchild Semiconductor part number
MV8W00.
2. See Figure 2.
3. See Figure 3.
4. Dark Current equivalent lux at 0 lux:
⎡
I
⎤
EL
= ⎢
OUT
⎥ ÷
(146
×
10
−
9
)
⎣
I
REF
⎦
4
5. For Flat Top (DU Package), I
REF
= 5824µA.
6. For Reverse Form (DR Package): I
REF
= 5985µA
E
LECTRICALS
E
LECTRICALS
Copyright
©
2005
Rev. 1.2, 2009-05-26
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 3
LX1973A
TM
®
Automotive Light Sensor
P
RODUCTION
D
ATA
S
HEET
TEST CIRCUITS
WWW .
Microsemi
.C
OM
V
DD
V
DD
White
LED
Part
OUT
GND
LX1973A
V
OUT
R
LOAD
V
DD
V
DD
White
LED
OUT
Part
810nm
GND
LX1973A
V
OUT
R
LOAD
Figure 2 –
Operational Voltage Measurement Circuit
Figure 3 –
IR Sensitivity Measurement Circuit
APPLICATION CIRCUITS
5V
5V
Part
LX1973A
10K
1µF
LX1800
SCL
To µP
SCD
GND
ADR
V
DD
REF
2.5V
Part
AIN
AOUT
DAC/ADC
BRT
HEADLAMP
CONTROLLER
LAMP
E
LECTRICALS
E
LECTRICALS
Figure 4 –
Typical Application
Copyright
©
2005
Rev. 1.2, 2009-05-26
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
LX1973A
TM
®
Automotive Light Sensor
P
RODUCTION
D
ATA
S
HEET
APPLICATIONS
G
ENERAL
D
ESCRIPTION
The LX1973A produces an output current that is sensitive to the level of ambient light that falls onto the
photosensitive area of the IC package. The sensitivity is amplified and compressed to provide ratio metric accuracy
across several decades. The sensitivity function is:
WWW .
Microsemi
.C
OM
I
OUT
(
P
)
=
I
ref
0.25
×
(
E
DARK
+
E
AMBIENT
)
lux
0.25
I
ref
= 113.8µA for the Flat Top package
I
ref
= 117µA for the Reverse Flat Top package
E
DARK
= dark current equivalent lux expressed in lux from a white LED point source.
E
AMBIENT
= ambient illumination expressed in lux from a white LED point source.
Copyright
©
2005
Rev. 1.2, 2009-05-26
Microsemi
Analog Mixed Signal Group
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
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