ALS-PDIC17-79NB-TR8 Datasheet, PDF (14/21 Pages) Everlight Electronics Co., Ltd – I2 Digital Ambient Light Sensor

Surface - Mount
I²C Digital Ambient Light Sensor
ALS-PDIC17-79NB/TR8
Similarly, setting the ALS-PDIC17-79NB integration time to an integer multiple of periodic noise signal
greatly improves the light sensor output signal in the presence of noise. The integration time, tint, of the
ALS-PDIC17-79NB is set by an external resistor Rext. The maximum detection range is inversely proportional
to the integration time; that means the longer integration time the lower detection range.
Rext
(KΩ)
50
(min.)
100
(recommended)
200
300
400
(max.)
Table 4. Rext Resistor Selection Guide
Integration time ( mS )
Detection range
( lux )
50
220,000
100
110,000
200
55,000
300
36,600
400
27,500
Resolution
( lux / count )
6.71
3.36
1.68
1.12
0.84
In order to achieve both 60Hz and 50Hz AC rejection, the integration time needs to be adjusted to
coincide with an integer multiple of the AC noise cycle times. To determine a suitable integration time, tint, that
will ignore the presence of both 60Hz and 50Hz noise, users can use the formula:
tint = n(1/60Hz) = m(1/50Hz), where n and m are integers.
n/m = 60Hz/50Hz = 6/5.
The first instance of integer values at which tint rejects both 60Hz and 50Hz is when m = 5,
and n = 6, thus,
tint = 6(1/60Hz) = 5(1/50Hz) = 100ms,
Rext = tint * (100kΩ/100ms) = 100kΩ, (see Table 4)
By populating Rext = 100kΩ, ALS-PDIC17-79NB defaults to 100ms integration time in continuous
operation mode, and will reject the presence of both 60Hz and 50Hz power line signals. When working in
one-time integration mode, the master must control the integration time to be an integer multiple of 100mS.
Everlight Electronics Co., Ltd.
Document No: DLS-xxxxxxx Rev1
14
http://www.everlight.com
Oct. 12, 2010