ISL29035_14 Datasheet, PDF (13/16 Pages) Intersil Corporation – Integrated Digital Light Sensor with Interrupt

ISL29035
between differing IR-content light sources, ISL29035 provides IR
channel which is programmed at COMMAND-1 (Reg0x0) to
measure IR level of differing IR-content light sources.
The ISL29035’s ADC output codes, DATA, are directly
proportional to the IR intensity received in the IR sensing.
DATA_IR =   E_IR
(EQ. 4)
Then EV accuracy can be found in Equation 5:
EV_Accuracy = KxDATA_EV +   DATA_IR
(EQ. 5)
Here, DATA_EV is the received ambient light intensity ADC output
codes. K is a resolution of visible portion. Its unit is Lux/count.
The typical values of K is 0.82. DATA_IR is the received IR intensity.
The constant  changes with the spectrum of background IR,
such as A, F2 and D65 (Notes 8, 9 and 10). The  also changes
with the ADC’s range and resolution selections. A typical for
range1 and range2 is -11292.86 and range3 and range4 is
2137.14 without IR tinted glass.
Noise Rejection
Electrical AC power worldwide is distributed at either 50Hz or
60Hz. Artificial light sources vary in intensity at the AC power
frequencies. The undesired interference frequencies are infused
on the electrical signals. This variation is one of the main sources
of noise for the light sensors. Integrating type ADC’s have
excellent noise-rejection characteristics for periodic noise
sources whose frequency is an integer multiple of the conversion
rate. By setting the sensor’s integration time to an integer
multiple of periodic noise signal, the performance of an ambient
light sensor can be improved greatly in the presence of noise. In
order to reject the AC noise, the integration time of the sensor
must to adjusted to match the AC noise cycle. For instance, a
60Hz AC unwanted signal’s sum from 0ms to k*16.66ms
(k = 1,2...k_i) is zero. Similarly, setting the device’s integration
time to be an integer multiple of the periodic noise signal greatly
improves the light sensor output signal in the presence of noise.
Suggested PCB Footprint
It is important that users check the “Surface Mount Assembly
Guidelines for Optical Dual Flat Pack No Lead (ODFN) Package”
before starting ODFN product board mounting: TB477
Board Mounting Considerations
For applications requiring the light measurement, the board
mounting location should be reviewed. The device uses an
Optical Dual Flat Pack No Lead (ODFN) package, which subjects
the die to mild stresses when the printed circuit (PC) board is
heated and cooled, which slightly changes the shape. Because of
these die stresses, placing the device in areas subject to slight
twisting can cause degradation of reference voltage accuracy. It
is normally best to place the device near the edge of a board, or
on the shortest side, because the axis of bending is most limited
in that location.
Layout Considerations
The ISL29035 is relatively insensitive to layout. Like other I²C
devices, it is intended to provide excellent performance even in
significantly noisy environments. There are only a few
considerations that will ensure best performance.
Route the supply and I²C traces as far as possible from all
sources of noise. Use two power-supply decoupling capacitors,
1µF and 0.1µF, placed close to the device.
Soldering Considerations
Convection heating is recommended for reflow soldering;
direct-infrared heating is not recommended. The plastic ODFN
package does not require a custom reflow soldering profile, and
is qualified to +260°C. A standard reflow soldering profile with a
+260°C maximum is recommended.
Temperature Coefficient
The limits stated for temperature coefficient (TC) are governed by
the method of measurement. The “Box” method is usually used
for specifying the temperature coefficient. The overwhelming
standard for specifying the temperature drift of a reference is to
evaluate the maximum voltage change over the specified
temperature range. This yields ppm/°C, and is calculated using
Equation 6:
TC
=
---------------------^V----^H----^I--^G-----^H-----–-----^V----^L---^O-----^W------------------------
V_NOMINAL  T_HIGH – T_LOW

10⁶
(EQ. 6)
where:
V_HIGH is the maximum reference voltage over the temperature
range.
V_LOW is the minimum reference voltage over the temperature
range.
V_NOMINAL is the nominal reference voltage at +25°C.
T_HIGH - T_LOW is the specified temperature range (°C)
Digital Inputs and Termination
The ISL29035 digital inputs are guaranteed to CMOS levels. The
internal register is updated on the rising edge of the clock. To
minimize reflections, proper termination should be
implemented. If the lines driving the clock and the digital inputs
are 50Ω lines, then 50Ω termination resistors should be placed
as close to the sensor inputs as possible, connected to the digital
ground plane (if separate grounds are used).
Typical Circuit
A typical application for the ISL29035 is shown in Figure 15. The
ISL29035’s I²C address is internally hard-wired as 1000100. The
device can be tied onto a system’s I²C bus, together with other
I²C compliant devices.
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FN8371.1
November 12, 2014