EPC111 EPC [Espros Photonics corp], EPC111 Datasheet - Page 5

• Manufacturer Part Number: EPC111
• Description: Fully integrated standalone light barrier driver & receiver
• Manufacturer: EPC [Espros Photonics corp]

Functional Description
Evaluation of single light pulse
For each single light pulse, received and detected by the LED, the threshold levels are processed according to the following principle to
propagate the output signals OUTN and OUTH resp. OUTN
threshold level, the pulse will be recognized as a valid pulse and the detection circuit sets the appropriate output signal OUTN
Pulse Modulated Operation (e.g. OUTN
The epc111/112 chip operates the LED and the receiver path on a pulse modulated concept. Thus, the LED is operated with short pulses
whereas the receiver channel does synchronous demodulation of the received light pulses by reading the current pulses of the photodiode.
This concept allows a very high sensitivity, high speed operation, and a high suppression of input ambient or foreign light (DC currents)
generated by sunlight or other DC light sources like light bulbs.
In order to eliminate interference caused by modulated light, e.g. a flashing light or by other light barriers, the input signal from the photodiode
is amplified, filtered, and processed by an integrated signal processor. If the photodiode signal meets the required frequency, pattern and
amplitude, the output(s) are triggered. The following timing diagram shows the basic concept.
It is in fact a digital filter which counts missing and non-missing pulses to change the ou tput state of OUTN or OUTH.
© 2011 ESPROS Photonics Corporation
Characteristics subject to change without notice
Emitter LED
Beam interrupted
Photo diode current I
OUTN
OUTN or OUTH
Signal output OUTN
Threshold levels:
Light reserve OUTH
INT
or OUTH
OUTN
OUTH
INT
yes
off
[V]
on
no
PD
INT
INT
I
PD
t
Pulse
int
t
F
to OUTN)
Light pulse detection
1
missing pulses
Release time
Figure 4: Pulse modulation concept
Figure 3: Pulse evaluation
2
t
Cycle
INT
and OUTH
n
M
5
INT
. As far the received light pulse signal exceeds the corresponding
t
t
t
I
PD
t
R
valid (non-missing) pulses
Light reserve detection
Response time
1
2
Datasheet epc111_112 - V2.2
n
V
epc111/112
t
t
t
INT
www.espros.ch
or OUTH
INT
.