ISL29023_14 Datasheet, PDF (11/14 Pages) Intersil Corporation – Integrated Digital Light Sensor with Interrupt

ISL29023
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, see TB477.
Board Mounting Consideration
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 ISL29023 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. R_EXT must be placed
as closely to the pin as possible to eliminate the stray
capacitance, which will greatly affect the performance of the
sensor.
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 8:
TC
=
---------------------^V----^H----^I--^G-----^H-----–-----^V----^L---^O-----^W------------------------
V_NOMINAL  T_HIGH – T_LOW

10⁶
(EQ. 8)
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 ISL29023 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 ISL29023 is shown in Figure 1. The
ISL29023’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.
2.25V TO 3.63V
R1 R2
R3
1.7V TO 3.63V
I²C MASTER
MICROCONTROLLER
SDA
SCL
INT
C1
10µF
C2
0.1µF
I²C SLAVE_0
1 _VDD
SDA ⁶
2 _GND
SCL ⁵
3 _REXT
INT ⁴
R_EXT
499k
ISL29023
I²C SLAVE_1
SDA
SCL
I²C SLAVE_n
SDA
SCL
FIGURE 15. ISL29023 TYPICAL SYSTEM DIAGRAM
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FN6691.4
May 1, 2014