ALS-PDIC17-57B-TR8_15 Datasheet, PDF (15/21 Pages) Everlight Electronics Co., Ltd – Digital Ambient Light Sensor

DATASHEET
SMD  I²C Digital Ambient Light Sensor
ALS-PDIC17-57B/TR8
Noise Rejection and Integration Time
In general, integrating type ADC’s have an excellent noise rejection characteristics for periodic noise sources
whose frequency is an integer multiple of the integration time. For instance, a 60Hz AC unwanted signal’s sum from 0ms
to n*16.66ms (n = 1, 2...ni) is zero. 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.
Integration time ( mS )
50
100
200
300
400
Detection range
( Lux )
88,400
44,200
22,200
14,500
11,100
Resolution
( Lux / Count )
2.7
1.35
0.68
0.45
0.34
Table 3 Detection Range Guide
In order to achieve both 120Hz and 100Hz 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 120Hz and 100Hz noise, users can use the formula:
tint = n(1/120Hz) = m(1/100Hz), where n and m are integers.
n/m = 120Hz/100Hz = 6/5.
The first instance of integer values at which tint rejects both 120Hz and 10Hz is when m = 5, and n = 6, thus,
tint = 6(1/120Hz) = 5(1/100Hz) = 50ms
Revi1si5on _Copy:_rig2_{ht © 2010, Everlight All Rights Reserved. Release Date : 5.27.2013. Issue No:}R_DLe_Sl_-e₀a₀₀s₀e₀₄D₉ at_Re:_e2_v.2013-06-0_w4_w0_w8_.:_e0_v6_e:_r0_li7_g._h0_t.com
LifecyclePhase:
Expired Period: Forever