TCS3771 datasheet(18/49 Pages) OSRAM

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ams Datasheet

Page 17

[v1-31] 2018-Apr-04

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TCS3771 − Principles of Operation

RGBC Operation

The RGBC engine contains RGBC gain control (AGAIN) and four

integrating analog-to-digital converters (ADC) for the RGBC

photodiodes. The RGBC integration time (ATIME) impacts both

the resolution and the sensitivity of the RGBC reading.

Integration of all four channels occurs simultaneously and upon

completion of the conversion cycle, the results are transferred

to the color data registers. This data is also referred to as channel

count. The transfers are double-buffered to ensure that invalid

data is not read during the transfer. After the transfer, the device

automatically moves to the next state in accordance with the

configured state machine.

Figure 20:

RGBC Operation

The registers for programming the integration and wait times

are a 2’s compliment values. The actual time can be calculated

as follows:

ATIME = 256 - Integration Time / 2.4ms

Inversely, the time can be calculated from the register value as

follows:

Integration Time = 2.4ms × (256 - ATIME)

For example, if a 100-ms integration time is needed, the device

needs to be programmed to:

256 - (100 / 2.4) = 256 - 42 = 214 = 0xD6

Conversely, the programmed value of 0xC0 would correspond

to:

(256 - 0xC0) × 2.4 = 64 × 2.4 = 154ms

TCS3771 Datasheet(PDF) 18 Page - OSRAM GmbH