LX1970 Mini Control Board
1/27/2005
Microsemi
Rev 1.0a Integrated Products
11861 Western Avenue, Garden Grove CA. 9284 1 714-898-8121 , FAX: 714-893-25 70
WWW.Microsemi .COM
LX1970 Light Sensor
INTEGRATED PRODUCTS
SCHEMATIC
R3
VDD
R1
R2
C2
4.7µF
VOUT
GND
C1
0.1µF
LX1970DU
VDD
NC
NC
SOURCE SINK
NC
NC
VSS
1
2
3
45
6
7
8
The LX1970 Mini Light Sensor Board can be used to convert a manual DC
voltage dimmer to a closed loop automatic dimmer. The resistor values can be
changed to fit the design requirements. The LX1970 output current is
proportional to the incident light intensity up to the point where either the
current source voltage compliance is exceeded or the light sensor saturates. See
the data sheet and applicatio n note for additional information.
()
[]
R2R1R2
VR1 IV
DDSRCOUT
+
×+×=
The value of R3 is typically less than 1K and is used as a power filter for the
LX1970 if the VDD line is excessively no isy.
With VDD = 3.0V, R1 = 150K, R2 = 30K and R3 = 0, the current output
voltage in total darkness is VDD x R2/ (R1 + R2) = 0.5V. The maximum output
voltage is approximately VDD – 0.3 = 2.7V, which is limited by the output
voltage compliance at a current of 2.7V x (R1 + R2) / (R1 x R2) = 108uA.
Protected by U.S. Patents: 6,787,757; Patents Pending.
PHOTO
PACKAGE PIN OUT
VSS
NC
NC
SNK
VDD
NC
NC
SRC
1
2
3
54
6
7
8
active area
DU
P
ACKAGE
(Top View)
FUNCTIONAL PIN DESCRIPTION
N
AME
D
ESCRIPTION
V
DD
Input Supply Voltage (Some boards wired with a RED pigtail.)
V
SS
Ground Reference for Power and Sign al O utput (Some boards wired with a BLACK pigtail.)
SNK Output Current Sink
SRC Output Current Source (Some boards wired with a YELLOW pigtail.)
L
LX
X1
19
97
70
0
