TMD2725 Datasheet, PDF (11/50 Pages) ams AG – The device features advanced proximity measurement

TMD2725 − Detailed Description
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
register. Signal from the photodiode is amplified, and offset
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
register address + 1.
ams Datasheet
[v1-11] 2016-Sep-20
Page 11
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