ISL29030A_14 Datasheet, PDF (11/16 Pages) Intersil Corporation – Low Power Ambient Light and Proximity Sensor with Intelligent Interrupt and Sleep Modes - Analog and Digital Out

ISL29030A
TABLE 15. ALS SENSITIVITY AT DIFFERENT RANGES
ALS_RANGE
α_RANGE
(Lux/Count)
0
0.0326
1
0.522
Table 15 shows two different scale factors: one for the low range
(ALS_RANGE = 0) and the other for the high range
(ALS_RANGE = 1).
Noise Rejection
Charge balancing ADCs have excellent noise-rejection
characteristics for periodic noise sources for which frequency is an
integer multiple of the conversion rate. 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. Since wall sockets
may output at 60Hz or 50Hz, the factory-set integration time is
100ms, which is the lowest common integer number of cycles for
both frequencies.
Proximity Detection of Various Objects
Proximity sensing relies on the amount of IR reflected back from
objects. A perfectly black object absorbs all light and reflects no
photons. The ISL29030A is sensitive enough to detect black ESD
foam, which reflects only 1% of IR. For biological objects, blonde
hair reflects more than brown hair, and customers may notice that
skin tissue is much more reflective than hair. IR penetrates into
the skin and is reflected or scattered back from within. As a result,
the proximity count peaks at contact and monotonically decreases
as skin moves away. The reflective characteristics of skin are very
different from that of paper.
Typical Circuit
A typical application for the ISL29030A is shown in Figure 5. The
ISL29030A I²C address is internally hardwired as 0b1000100.
The device can be tied onto a system I²C bus together with other
I²C compliant devices.
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.
Suggested PCB Footprint
It is important that users see TB477, “Surface Mount Assembly
Guidelines for Optical Dual FlatPack No Lead (ODFN) Package”
before starting ODFN product board mounting.
Layout Considerations
The ISL29030A is relatively insensitive to layout. Like other I²C
devices, it is intended to provide excellent performance, even in
significantly noisy environments. To ensure best performance,
route the supply and I²C traces as far as possible from all
sources of noise, and place a 0.1µF and 1µF power supply
decoupling capacitor close to the device.
ALS Sensor Window Layout
Special care should be taken to ensure that the sensor is
uniformly illuminated, as shown in Figure 16, “8 LD ODFN
SENSOR LOCATION OUTLINE - DIMENSIONS IN mm”. Shadows
from window openings that affect uniform illumination can
distort measurement results.
V_DD
R1
10kΩ
R2
R3
10kΩ 10kΩ
V_IR-LED
V_{I2C_PULL-UP}
I²C MASTER
MICROCONTROLLER
INT
SDA
SCL
V
SLAVE_0
1 _IALS
3.5kΩ
IRDR ⁸
C1
C2
1µF
0.1µF
2 _VDD
3 _GND
7
INT
SDA ⁶
4
5
REXT SCL
REXT ISL29030A
499kΩ
SLAVE_1
SDA
SCL
I²C SLAVE_n
SDA
SCL
FIGURE 5. ISL29030A TYPICAL CIRCUIT
11
FN7722.2
November 12, 2012