TSL2671

DIGITAL PROXIMITY DETECTOR

TAOS118 − JANUARY 2011

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Copyright

E 2011, TAOS Inc.

The LUMENOLOGY

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www.taosinc.com

Functional Block Diagram

SDA

INT

SCL

LDR

Wait Control

Prox

ADC

Prox Control

Prox

Data

IR LED Constant

Current Sink

Prox

Integration

Upper Limit

Lower Limit

Interrupt

GND

CH0

CH1

Detailed Description

The TSL2671 light-to-digital device provides on-chip photodiodes, integrating amplifiers, ADCs, accumulators,

photodiode (CH0), which is responsive to both visible and infrared light, and a channel 1 photodiode (CH1),

which is responsive primarily to infrared light. Proximity detection can occur using either or both photodiodes.

Two integrating ADCs simultaneously convert the amplified photodiode currents into 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.

Proximity detection requires only a single external IR LED. An internal LED driver can be configured to provide

a constant current sink of 12.5 mA, 25 mA, 50 mA, or 100 mA of current. No external current limiting resistor

is required. The number of proximity LED pulses can be programmed from 1 to 255 pulses. Each pulse has a

16-

μs period. This LED current, coupled with the programmable number of pulses, provides a 2000:1

contiguous dynamic range.

connection to a microcontroller or embedded controller. The digital output of the device is inherently more

immune to noise when compared to an analog interface.

The device 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 proximity

value. An interrupt is generated when the value of a 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.