TSL27711FN TAOS, TSL27711FN Datasheet - Page 12

• Manufacturer Part Number: TSL27711FN
• Description: Light to Digital Converters Light to Digital w/Proximity
• Manufacturer: TAOS

Specifications of TSL27711FN

• Data Bus Width: 16 bit
• Peak Wavelength: 640 nm, 850 nm
• Maximum Operating Frequency: 795 KHz
• Operating Supply Voltage: 2.4 V to 3.6 V
• Operating Current: 175 uA
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: - 30 C
• Interface Type: I2C
• Maximum Fall Time: 300 ns
• Maximum Rise Time: 300 ns
• Mounting Style: SMD/SMT
• Resolution: 16 bit
• Package / Case: DFN-6
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

TSL2771
LIGHT-TO-DIGITAL CONVERTER
with PROXIMITY SENSING
TAOS100A − FEBRUARY 2010
Fluorescent Ripple Rejection
Recommended ALS Operations
12
Copyright E 2010, TAOS Inc.
There are many factors that will impact the decision on which value to use for integration time and gain. One
of the first factors is 50/60-Hz ripple rejection for fluorescent lighting. The programmed value needs to be
multiples of 10 / 8.3 ms, or the half cycle time. Both frequencies can be rejected with a programmed value of
50 ms (ATIME=0xED). With this value, the resolution will be 1.3 lux per count. If higher resolution is needed,
a longer integration time may be needed. In this case, the integration time should be programmed in multiples
of 50.
With the programming versatility of the integration time and gain, it can be difficult to understand when to use
the different modes. Figure 8 shows a plot of the IRF equations. Figure 9 shows a log-log plot of the lux vs.
integration time and gain with a spectral factor of unity and no IR present.
The maximum illuminance that can be measured is approximately 19 k-lux with no IR present. The intercept
with a count of 1 shows the resolution of each setting. The lux values in the table increase as the SF increases
(spectral attenuation increases). For example, if a 10% transmissive glass is used, the lux values would all be
multiplied by 10. The lux values in the table decrease as the IR Factor decreases. For example, with a 10% IR
Factor, which corresponds to a strong incandescent light, the Lux value would need to be divided by 10.
The light level is the next determining factor for configuring device settings. Under bright conditions, the count
will be fairly high. If a low light measurement is needed, a higher gain and/or longer integration time will be
needed. As a general rule, it is recommended to have a clear channel count of at least 10 to accurately apply
the lux equation.
The digital accumulation is limited to 16 bits, which occurs at an integration time of 173 ms. This is the maximum
recommended programmed integration time before increasing the gain. (150 ms is the maximum to reduce the
fluorescent ripple.)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
1
0
0
Fluorescent
0.2
CH1 / CH0 Ratio
Figure 8
CH1 /CH0 Ratio
ATTENUATION
0.4
vs.
Incandescent
0.6
r
www.taosinc.com
0.8
100 k
1000
0.01
10 k
100
0.1
10
1
1
GAIN AND INTEGRATION TIME
r
LUX (with NO IR)
Figure 9
100
Counts
The LUMENOLOGY r Company
to
10000