TMD27721 datasheet(22/59 Pages) AMSCO

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ams Datasheet, Confidential

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[v1-20] 2014-Jul-21

TMD2772/ TMD2772WA − Principles of Operation

controlled by the proximity ADC conversion time (PTIME) which

is programmable from 1 to 256 2.73ms time units. However,

depending on the application, scaling the proximity data will

equally scale any accumulated noise. Therefore, in general, it is

recommended to leave PTIME at the default value of one 2.73ms

ADC conversion time (0xFF).

In many practical proximity applications, a number of optical

system and environmental conditions can produce an offset in

the proximity measurement result. To counter these effects, a

proximity offset (POFFSET ) is provided which allows the

proximity data to be shifted positive or negative. Additional

information on the use of the proximity offset feature is

provided in available ams application notes.

Once the first proximity cycle has completed, the proximity

valid (PVALID) bit in the Status register will be set and remain

set until the proximity detection function is disabled (PEN).

For additional information on using the proximity detection

function behind glass and for optical system design guidance,

please see available ams application notes.

Interrupts

The interrupt feature simplifies and improves system efficiency

by eliminating the need to poll the sensor for light intensity or

proximity values outside of a user-defined range. While the

interrupt function is always enabled and its status is available

in the status register (0x13), the output of the interrupt state

can be enabled using the proximity interrupt enable (PIEN) or

ALS interrupt enable (AIEN) fields in the enable register (0x00).

Four 16-bit interrupt threshold registers allow the user to set

limits below and above a desired light level and proximity

range. An interrupt can be generated when the ALS CH0 data

(C0DATA) falls outside of the desired light level range, as

determined by the values in the ALS interrupt low threshold

registers (AILTx) and ALS interrupt high threshold registers

(AIHTx). Likewise, an out-of-range proximity interrupt can be

generated when the proximity data (PDATA) falls below the

proximity interrupt low threshold (PILTx) or exceeds the

proximity interrupt high threshold (PIHTx).

It is important to note that the thresholds are evaluated in

sequence, first the low threshold, then the high threshold. As a

result, if the low threshold is set above the high threshold, the

high threshold is ignored and only the low threshold is

evaluated.

To further control when an interrupt occurs, the device provides

a persistence filter. The persistence filter allows the user to

specify the number of consecutive out-of-range ALS or

proximity occurrences before an interrupt is generated. The

Interrupt register (0x0C) allows the user to set the ALS

persistence filter (APERS) and the proximity persistence filter

(PPERS) values. See the “Interrupt Register (0x0C)” on page 35

for details on the persistence filter values. Once the persistence

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