TMD27253 datasheet(11/50 Pages) AMSCO

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[v1-11] 2016-Sep-20

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TMD2725 − Detailed Description

Proximity

Proximity results are affected by three fundamental factors: the

integrated IR LED emission, IR reception, and environmental

factors, including target distance and surface reflectivity.

The IR reception signal path begins with IR detection from a

photodiode and ends with the 8-bit proximity result in PDATA

adjusted to optimize performance. Offset correction or

cross-talk compensation is accomplished by adjustment to the

POFFSET register.

The analog circuitry of the device applies the offset value as a

subtraction to the signal accumulation; therefore a positive

offset value has the effect of decreasing the results.

Ambient Light Sensing, ALS

The ALS reception signal path begins as photodiodes receive

filtered light and ends with the 16-bit results in the

PHOTOPICL/H and ALS_IRL/H registers. The Photopic

photodiode is filtered with a UV and IR filter. The ALS_IR

photodiode is filtered to receive only IR. Signal from the

photodiodes simultaneously accumulate for a period of time

set by the value in ATIME before the results are available. Gain

is adjustable from 1x to 64x to facilitate operation over a wide

range of lighting conditions. Custom LUX equations are used to

calculate the amount of ambient light, as well as, determine the

light type (e.g. LED, fluorescent, incandescent, etc.) using the

two ALS results.

I²C Characteristics

The device uses I²C serial communication protocol for

communication. The device supports 7-bit chip addressing and

both standard and fast clock frequency modes with a chip

address of 0x39. Read and Write transactions comply with the

standard set by Philips (now NXP).

Internal to the device, an 8-bit buffer stores the register address

location of the desired byte to read or write. This buffer

auto-increments upon each byte transfer and is retained

between transaction events (I.e. valid even after the master

issues a STOP command and the I²C bus is released). During

consecutive Read transactions, the future/repeated I²C Read

transaction may omit the memory address byte normally

following the chip address byte; the buffer retains the last

Detailed Description

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