TSL2580CS datasheet(34/53 Pages) OSRAM

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ams Datasheet

Page 33

[v1-00] 2016-Apr-05

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TSL2580, TSL2581 − Application Information: Software

set to 0000b. Either Level or SMBus Alert style can be used. An

interrupt will be generated upon completion of each

conversion. The interrupt threshold registers are ignored.

Calculating Lux

The TSL258x is intended for use in ambient light detection

applications such as display backlight control, where

adjustments are made to display brightness or contrast based

on the brightness of the ambient light, as perceived by the

human eye. Conventional silicon detectors respond strongly to

infrared light, which the human eye does not see. This can lead

to significant error when the infrared content of the ambient

light is high, such as with incandescent lighting, due to the

difference between the silicon detector response and the

brightness perceived by the human eye.

This problem is overcome in the TSL258x through the use of

two photodiodes. One of the photodiodes (channel 0) is

sensitive to both visible and infrared light, while the second

photodiode (channel 1) is sensitive primarily to infrared light.

An integrating ADC converts the photodiode currents to digital

outputs. Channel 1 digital output is used to compensate for the

effect of the infrared component of light on the channel 0

digital output. The ADC digital outputs from the two channels

are used in a formula to obtain a value that approximates the

human eye response in the commonly used Illuminance unit of

Lux:

Chipscale Package

For CH1/CH0 = 0.00 to 0.25

Lux = 0.105 CH0 - 0.208 CH1

For CH1/CH0 = 0.25 to 0.38

Lux = 0.1088 CH0 - 0.2231 CH1

For CH1/CH0 = 0.38 to 0.45

Lux = 0.0729 CH0 - 0.1286 CH1

For CH1/CH0 = 0.45 to 0.60

Lux = 0.060 CH0 - 0.10 CH1

For CH1/CH0 > 0.60

Lux/CH0 = 0

ODFN Package

For CH1/CH0 = 0.00 to 0.30

Lux = 0.130 CH0 - 0.240 CH1

For CH1/CH0 = 0.30 to 0.38

Lux = 0.1649 CH0 - 0.3562 CH1

For CH1/CH0 = 0.38 to 0.45

Lux = 0.0974 CH0 - 0.1786 CH1

For CH1/CH0 = 0.45 to 0.54

Lux = 0.062 CH0 - 0.100 CH1

For CH1/CH0 > 0.54

Lux/CH0 = 0

The formulas shown above were obtained by optical testing

with fluorescent and incandescent light sources, and apply only

to open-air applications. Optical apertures (e.g. light pipes) will

affect the incident light on the device.

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