5

FN6619.0

March 3, 2009

Principles of Operation

Photodiodes and ADC

The ISL29018 contains two photodiode arrays which convert

light into current. The spectral response for ambient light

sensing and IR sensing is shown in Figure 6 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

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 9.

The built-in ADC offers user flexibility in integration time or

conversion time. Integration time is determined by an internal

the ADC. A good balancing act of integration time and

resolution depending on the application is required for optimal

results.

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 ISL29018 initial operation is at the power-down mode

after a supply voltage is provided. The data registers contain

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 ISL29018 will

continuously do ADC conversion with light or proximity

measurement. It will continuously update the data registers

with the latest conversion data. It will go to the power-down

Ambient Light, IR and Proximity Sensing

There are six operational modes in ISL29018: 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 and

programmable continuous proximity sensing. These six

modes can be programmed in series to fulfill the application

SDA and INT Current Sinking Capability

4

5

mA

IRDR Source Current

IS<1:0> = 0 (Note 5)

15

Ω at IRDR pin

100

mA

IRDR Source Current

IS<1:0> = 1 (Note 5)

44

50

58

mA

IRDR Source Current

IS<1:0> = 2 (Note 5)

25

mA

IRDR Source Current

IS<1:0> = 3 (Note 5)

12.5

mA

Voltage Head Room of IRDR Pin

V

tr

Rise Time for IRDR Source Current

35

ns

tf

Fall Time for IRDR Source Current

10

ns

IR LED Modulation Frequency

Freq = 0 (Note 5)

DC

kHz

IR LED Modulation Frequency

Freq = 1 (Note 5)

360

kHz

IS<1:0> = 0, Freq = 0 (Note 5)

101

mA

IS<1:0> = 0, Freq = 1 (Note 5)

51

mA

Duty Cycle

Duty Cycle of IR LED Modulation

50

%

PROX-IR

PROX

Differential ADC Output of IR and Proximity

Sensing With Object Far Away to Provide

No Reflection

IR and proximity sensing with Range 2 and Scheme 0;

15

Ω @ IRDR pin, IS<1:0> = 0, Freq = 0; E = 210 lux,

Sunlight.

1.0

%

NOTES:

3. 550nm green LED is used in production test. The 550nm LED irradiance is calibrated to produce the same DATA count against an illuminance

level of 300 lux fluorescent light.

4. 850nm infrared LED is used in production test. The 850nm LED irradiance is calibrated to produce the same DATA_IR count against an illuminance

level of 210 lux sunlight at sea level.

5. See “Register Set” on page 7.

Electrical Specifications

specified. (Continued)

PARAMETER

DESCRIPTION

CONDITION

MIN

TYP

MAX

UNIT

ISL29018