ISL29030A

11

FN7722.2

November 12, 2012

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

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

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

devices, it is intended to provide excellent performance, even in

significantly noisy environments. To ensure best performance,

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.

TABLE 15. ALS SENSITIVITY AT DIFFERENT RANGES

ALS_RANGE

(Lux/Count)

0

0.0326

1

0.522

1

GND

3

REXT

4

SDA

INT

7

IRDR

8

ISL29030A

R1

10kΩ

R2

10kΩ

REXT

499kΩ

MICROCONTROLLER

INT

SDA

SLAVE_0

SLAVE_1

SCL

SDA

SCL

SDA

6

R3

10kΩ

SCL

2

VDD

5

C2

0.1µF

FIGURE 5. ISL29030A TYPICAL CIRCUIT

SCL

C1

1µF

V

3.5kΩ