TMD3721 datasheet(15/89 Pages) OSRAM

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Page 14

Datasheet, Public

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[v3-00] 2023-May-26

TMD3721 − Detailed Description

Figure 14:

Proximity Integration and Data Sampling in TMD3721

Color and Ambient Light Sensing

The color and ALS reception signal path begins as the

photodiodes receive filtered light and ends with 16-bit results.

In addition to the RGB absorption filters applied to RGB

channels, there is also a UV-IR blocking filter applied to all ALS

channels including Clear channel for accurately measuring

ambient light levels. Signals from all photodiodes are

simultaneously accumulated for a period of time set by the

value in ATIME (or ASP1, ASP2 if enabled) before the results are

available. Gain is adjustable in the range of 1x to 4096x to

facilitate operation over a wide range of lighting conditions,

including under dark glass or OLED displays with low optical

transmissivity. Based on the optical glass or OLED display used

over of the device, custom equations based on the ALS data are

empirically derived to calculate the amount of ambient light

and the correlated color temperature.

The ALS integration is designed to be able to synchronize to the

display VSYNC signal with a delay time defined by ASD (when

AVSYNC_EN=1). ASD must be programmed greater than the ALS

initialization time, otherwise ASD is ignored. ALS initialization

time requires 24 ALS clocks, resulting in 32.568μs (typical). If

ASP1, ASP2 are enabled, the device allows for quick sampling

over the integration time (ATIME) in intervals of ASP1, ASP2 and

stores the ALS data in the FIFO. With ASP1 and ASP2 disabled,

the ALS data will be collected once at the end of the full ALS

integration time. AWTIME allows the addition of a wait time and

defines the ALS repetition period. The subsequent ALS cycle

will occur on the first VSYNC after the end of the AWTIME period,

plus the delay defined by ASD.

Figure 15 shows an example of ALS integration and data

sampling for the TMD3721.

PTIME

PSD

PTIME

PSD

PTIME

Prox_Init_Time

Temp_Meas

(if enabled)

PROX_DATA_AVG loop

PSD

PTIME

Prox_Init_Time

Start s hifts

PVSYNC_EN=0

Start s hifts

PVSYNC_EN=0

Start s hifts

PVSYNC_EN=0

Start s hifts

PVSYNC_EN=0

Start s hifts

PVSYNC_EN=0

PON=1

PEN=1

PWEN=1

PVSYNC=1

VSYNC

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