ISL29034 Datasheet, PDF (6/14 Pages) Intersil Corporation – Wide dynamic range1

ISL29034
Typical Performance Curves
1.2
1.0
HUMAN EYE
0.8
AMBIENT LIGHT SENSOR
0.6
0.4
0.2
0
300 400 500 600 700 800 900 1000 1100
WAVELENGTH (nm)
FIGURE 6. NORMALIZED SPECTRAL RESPONSE FOR AMBIENT
LIGHT SENSING
1.2
1.0
0.8
0.6
0.4
0.2
0-60 _{-50 -40 -30 -20 -10 0 10 20 30 40 50 60}
ANGLE (°)
FIGURE 7. NORMALIZED RADIATION PATTERN
14
12
1000 LUX RANGE
10
8
6
4
2
0
-60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100
TEMPERATURE (°C)
FIGURE 8. TEMPERATURE TEST IN DARK CONDITION
1000
800
1000 LUX RANGE
600
400
200
0
0
200
400
600
800
AMBIENT LIGHT (LUX)
FIGURE 9. ALS TRANSFER FUNCTION
1000
Principles of Operation
Photodiodes and ADC
The ISL29034 contains two photodiode arrays, which convert light
into current. A typical spectral response for ambient light sensing is
shown in Figure 6 on page 6. After light is converted to current
during the light signal process, the current output is converted to
digital by a built-in 16-bit Analog-to-Digital Converter (ADC). An I²C
command reads the ambient light intensity in counts.
The converter is a charge-balancing integrating type 16-bit ADC. The
chosen method for conversion is best for converting small current
signals in the presence of an AC periodic noise. A 105ms integration
time, for instance, highly rejects 50Hz and 60Hz power line noise
simultaneously.
The integration time of the built-in ADC is determined by the internal
oscillator, and the n-bit (n = 4, 8, 12, 16) counter inside the ADC. A
good balancing act of integration time and resolution (depending on
the application) is required for optimal results.
The ADC has I²C programmable range select to dynamically
accommodate various lighting conditions. For very dim
conditions, the ADC can be configured at its lowest range
(Range 0) in the ambient light sensing.
Low-Power Operation
The ISL29034 initial operation is at the power-down mode after a
supply voltage is provided. The data registers contain the default
value at 0. When the ISL29034 receives an I²C command to do a
one-time measurement from an I²C master, it will start the ADC
conversion with light sensing. It will go to the power-down mode
automatically after one conversion is finished and keep the
conversion data available for the master to fetch anytime
afterwards. The ISL29034 will continuously do ADC conversion
with light sensing if it receives an I²C command of continuous
measurement. It will continuously update the data registers with
the latest conversion data. It will go to the power-down mode
after it receives the I²C command of power-down.
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6
FN8370.2
August 19, 2016