TCS3471

COLOR LIGHT-TO-DIGITAL CONVERTER

TAOS115 − MARCH 2011

8

r

r

Copyright

E 2011, TAOS Inc.

The LUMENOLOGY

r Company

www.taosinc.com

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.

AGAIN(r 0x0F, b1:0)

1

y, 4y, 16y, 60y Gain

CDATAH(r 0x15), CDATA(r 0x14)

Clear ADC

Red ADC

Green ADC

Blue ADC

Clear Data

Red Data

Green Data

Blue Data

RGBC Control

Blue

Green

Red

Clear

RDATAH(r 0x17), RDATA(r 0x16)

GDATAH(r 0x19), GDATA(r 0x18)

BDATAH(r 0x1B), BDATA(r 0x1A)

ATIME(r 1)

2.4 ms to 700 ms

Figure 7. 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 / 2.4 ms

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

Integration Time = 2.4 ms

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)