epc120

Fully integrated Light-Barrier Chips with 2-Wire Bus Interface

General Description

The epc120 is a general purpose, fully integrated self-contained

CMOS circuit to be used in light-barrier applications. The chips

contain a controller which drives an LED, typically an IR-LED. The

LED is used in a pulsed mode to increase the signal-to-noise ratio

even when there is very strong sunlight biasing the photo diode.

It contains also a high sensitive photo diode amplifier and a signal

conditioning circuitry to cancel unwanted environmental light including

strong sunlight and pulsed light sources. The receiver is built around

a synchronous demodulator circuitry. Two output signals with a

different threshold level are implemented in order to trigger the light

barriers output or to indicate light reserve.

The chips also include a power supply circuitry to establish all

internally required voltages from the 2-wire bus.

They contain a 2-wire communication interface which is capable to

operate as many as 1023 devices on a 2-wire bus at a speed of up to

2MBit/s over the power supply. This feature allows to design of a

distributed light barrier system.

Features



Fully integrated light barrier chip



Needs just a photo diode and an LED with an LED driver



Configurable



High speed 2-wire bus



Integrated clock generator



CSP10 package with very small footprint or

standard QFN16 package available



Versions without 2-wire bus interface available (epc11x family)

Applications



Light barriers ranging from millimeters to tens of meters



Smoke detectors



Liquid detectors

Functional Block Diagram

Functional Block diagram epc70x

LST

Parameter

Memory

2-wire COM

Interface

2-wire COM

Interface

SO

SI

EN

CS

VDD33

PD

19.10.2010

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.

LED

D1

V

LED

f

VDD18

Signal

Processor

Processor

SPI

Controller

GND

VDD

LED

SCK

© 2011 ESPROS Photonics Corporation

Characteristics subject to change without notice

1

Datasheet epc12x - V2.1

www.espros.ch