ISL29011_14 Datasheet, PDF (7/19 Pages) Intersil Corporation – Digital Ambient Light Sensor and Proximity Sensor with Interrupt Function

ISL29011
FIGURE 1. I²C TIMING DIAGRAM
Principles of Operation
Photodiodes and ADC
The ISL29011 contains two photodiode arrays which convert
light into current. The spectral response for ambient light sensing
and IR sensing is shown in Figure 8 in the performance curves
section. 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 or IR 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 100ms
integration time, for instance, highly rejects 50Hz and 60Hz power
line noise simultaneously. See “Integration and Conversion Time”
on page 11.
The built-in ADC offers user flexibility in integration time or
conversion time. Integration time is determined by an internal
oscillator (f_OSC), 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 1) in the
ambient light sensing. For very bright conditions, the ADC can be
configured at its highest range (Range 4) in the proximity sensing.
Low-Power Operation
The ISL29011 initial operation is at the power-down mode after a
supply voltage is provided. The data registers contain the default
value of zero. When the ISL29011 receives an I²C command to
do a one-time measurement from an I²C master, it will start ADC
conversion with light or proximity 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 ISL29011 will continuously do ADC
conversion with light or proximity sensing, if it receives an I²C
command of continuous measurement. It will continuously
update the data registers with the latest conversion data, and It
will go to the power-down mode after it receives the I²C
command of power-down.
Ambient Light, IR and Proximity Sensing
There are six operational modes in ISL29011: Programmable ALS
once with auto power-down, programmable IR sensing once with
auto power-down, programmable proximity sensing once with auto
power-down, programmable continuous ALS sensing,
programmable continuous IR sensing, programmable continuous
proximity sensing. These six modes can be programmed in series
to fulfill the application needs. The detailed program configuration
is listed in “Register Set” on page 10.
When the part is programmed for ambient light sensing, the
ambient light with wavelength within the “Ambient Light
Sensing” spectral response curve in Figure 8 is converted into
current. With ADC, the current is converted to an unsigned n-bit
(up to 16 bits) digital output.
When the part is programmed for infrared (IR) sensing, the IR
light with wavelength within the “IR or Proximity Sensing”
spectral response curve on Figure 8 is converted into current.
With ADC, the current is converted to an unsigned n-bit
(up to 16 bits) digital output.
When the part is programmed for proximity sensing, the external
IR LED is turned on by the built-in IR LED driver through the IRDR
pin. The amplitude of the IR LED current and the IR LED
modulation frequency can be programmed through Command
Register II. When the IR from the LED reaches an object and gets
reflected back, the reflected IR light with wavelength within the
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FN6467.6
May 1, 2014