6

FN6467.4

May 5, 2011

Principles of Operation

Photodiodes and ADC

The ISL29011 contains two photodiode arrays which convert

light into current. The spectral response for ambient light

sensing and IR sensing is shown in Figure 7 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 10.

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

Set-up Time for STOP Condition

600

ns

Bus Free Time Between a STOP and START

Condition

1300

ns

Capacitive Load for Each Bus Line

400

pF

SDA and SCL system bus pull-up resistor

1k

Ω

Data Valid Time

0.9

µs

Data Valid Acknowledge Time

0.9

µs

Noise Margin at the LOW Level

0.1VDD

V

Noise Margin at the HIGH Level

0.2VDD

V

NOTE:

I2C Electrical Specifications

tolerance, 16-bit ADC operation (Note 9).

PARAMETER

DESCRIPTION

CONDITION

MIN

TYP MAX UNIT

ISL29011