ISL29003IROZ-T7 View Datasheet(PDF) - Intersil

Part Name

Description

Manufacturer

ISL29003IROZ-T7

Light-to-Digital Output Sensor with High Sensitivity, Gain Selection, Interrupt Function and I2C Interface

Intersil 

ISL29003

TABLE 14. SOLUTION1 SUMMARY TO EXAMPLE DESIGN

PROBLEM

DESIGN PARAMETER

VALUE

tint

REXT

Gain/Range Mode

100ms

50kΩ

Range1 = 1000 lux

FSR

# of clock cycles

2000 lux

216

Transfer Function

E

=

D-----A-----T----A--

216

×

2000

lux

Solution 2

Using External Timing Mode

From Solution 1, the desired integration time is 100ms. Note

that the REXT resistor only determines the inter oscillator

frequency when using external timing mode. Instead, the

integration time is the time between two sync_iic commands

sent through the I2C. The programmer determines how

many I2C clock cycles to wait between two external timing

commands.

iI2C = fI2C*tint = number of I2C clock cycles

iI2C = 10kHz *100ms

iI2C = 1,000 I2C clock cycles. An external sync_iic command

sent 1,000 cycles after another sync_iic command rejects

both 60Hz and 50Hz AC noise signals.

Next, is to pick an arbitrary REXT = 100kΩ and to choose the

Gain/Range Mode. For a maximum 500 lux, Range1 is

adequate. From Equation 3:

FSR

=

1000

lux

1----0---0----k---Ω---

100 k Ω

FSR = 1000 lux

The effective transfer function becomes:

E

=

--------D-----A----T----A----------

COUNTER

×

1000

lux

DATA is the sensor reading data located in data registers

04(hex) and 05(hex)

COUNTER is the timer counter value data located in data

registers 06(hex) and 07(hex). In this sample problem,

COUNTER = 1000.

TABLE 15. SOLUTION2 SUMMARY TO EXAMPLE DESIGN

PROBLEM

DESIGN PARAMETER

VALUE

tint

REXT

Gain/Range Mode

100ms

100kΩ

Range1 = 1000 lux

FSR

1000 lux

# of clock cycles

COUNTER = 1000

Transfer Function

E

=

--------D-----A----T----A----------

COUNTER

×

1 000

lux

IR Rejection

Any filament type light source has a high presence of infrared

component invisible to the human eye. A white fluorescent

lamp, on the other hand has a low IR content. As a result,

output sensitivity may vary depending on the light source.

Maximum attenuation of IR can be achieved by properly

scaling the readings of Diode1 and Diode2. The user obtains

data reading from sensor Diode1 (D1), which is sensitive to

visible and IR, then reading from sensor Diode2 (D2), which is

mostly sensitive from IR. The graph in Figure 8 shows the

effective spectral response after applying Equation 19 of the

ISL29003 from 400nm to 1000nm. Equation 19 describes the

method of cancelling IR in internal timing mode.

D3 = n(D1 – kD2)

(EQ. 19)

Where:

data = lux amount in number of counts less IR presence

D1 = data reading of Diode1

D2 = data reading of Diode2

n = 1.85. This is a fudge factor to scale back the sensitivity

up to ensure Equation 4 is valid.

k = 7.5. This is a scaling factor for the IR sensitive Diode2.

Flat Window Lens Design

A window lens will surely limit the viewing angle of the

ISL29003. The window lens should be placed directly on top

of the device. The thickness of the lens should be kept at

minimum to minimize loss of power due to reflection and

also to minimize loss of loss due to absorption of energy in

the plastic material. A thickness of t = 1mm is recommended

for a window lens design. The bigger the diameter of the

window lens, the wider the viewing angle is of the ISL29003.

Table 16 shows the recommended dimensions of the optical

window to ensure both 35° and 45° viewing angle. These

dimensions are based on a window lens thickness of 1.0mm

and a refractive index of 1.59.

WINDOW LENS

t

∅

DTOTAL

D1

ISL29003

DLENS

∅ = Viewing angle

FIGURE 4. FLAT WINDOW LENS

10

FN7464.5

August 8, 2008

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