TCS3771

COLOR LIGHT-TO-DIGITAL CONVERTER

with PROXIMITY SENSING

TAOS110A − MARCH 2011

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Copyright

E 2011, TAOS Inc.

The LUMENOLOGY

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www.taosinc.com

The proximity function is targeted specifically towards battery-powered mobile devices, LCD monitor, laptop,

and flat-panel television applications. In cell phones, the proximity detection can detect when the user positions

the phone close to their ear. The device is fast enough to provide proximity information at a high repetition rate

needed when answering a phone call. It can also detect both close and far distances so the application can

implement more complex algorithms to provide a more robust interface. In laptop or monitor applications, the

product is sensitive enough to determine whether a user is in front of the laptop using the keyboard or away from

the desk. This provides both improved green power saving capability and the added security to lock the

computer when the user is not present.

Functional Block Diagram

SDA

INT

SCL

LDR

Wait Control

Prox

ADC

Prox Control

Prox

Data

IR LED Constant

Current Sink

Clear ADC

Prox

Integration

Upper Limit

Upper Limit

Lower Limit

Lower Limit

Interrupt

GND

Red ADC

Green ADC

Blue ADC

Clear Data

Red Data

Green Data

Blue Data

RGBC Control

Blue

Green

Red

Clear

Detailed Description

The TCS3771 light-to-digital device contains a 4

× 4 photodiode array, integrating amplifiers, ADCs,

× 4 photodiode array

is composed of red-filtered, green-filtered, blue-filtered, and clear photodiodes — four of each type. Four

integrating ADCs simultaneously convert the amplified photodiode currents to a digital value providing up to 16

bits of resolution. Upon completion of the conversion cycle, the conversion result is transferred to the data

registers. The transfers are double-buffered to ensure that the integrity of the data is maintained.

connection to a microcontroller or embedded controller.

The TCS3771 provides a separate pin for level-style interrupts. When interrupts are enabled and a pre-set value

is exceeded, the interrupt pin is asserted and remains asserted until cleared by the controlling firmware. The

interrupt feature simplifies and improves system efficiency by eliminating the need to poll a sensor for a light

intensity or proximity value. An interrupt is generated when the value of an RGBC or proximity conversion

exceeds either an upper or lower threshold. In addition, a programmable interrupt persistence feature allows

the user to determine how many consecutive exceeded thresholds are necessary to trigger an interrupt.

Interrupt thresholds and persistence settings are configured independently for both RGBC and proximity.