TMD2672

DIGITAL PROXIMITY DETECTOR

TAOS149C − AUGUST 2012

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Copyright

E 2012, TAOS Inc.

The LUMENOLOGY

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www.taosinc.com

Functional Block Diagram

SDA

INT

SCL

Wait Control

Prox

ADC

Prox Control

Prox

Data

IR LED Constant

Current Sink

Prox

Integration

Upper Limit

Lower Limit

Interrupt

GND

Channel 1

LEDA

LEDK

LDR

Channel 0

Detailed Description

A fully integrated proximity detection solution is provided with an 850-nm IR LED, LED driver circuit, and

proximity detection engine. An internal LED driver (LDR) pin, is externally connected to the LED cathode (LEDK)

to provide a controlled LED sink current. This is accomplished with a proprietary current calibration technique

that accounts for all variances in silicon, optics, package, and most important, IR LED output power. This

eliminates or greatly reduces the need for factory calibration that is required for most discrete proximity sensor

solutions. The device is factory calibrated to achieve a proximity count reading at a specified distance with a

specific number of pulses. In use, the number of proximity LED pulses can be programmed from 1 to 255 pulses,

which allows different proximity distances to be achieved. Each pulse has a 16-

μs period, with a 7.2-μs on time.

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.