epc110
R
Stab
VDD
VDD
epc100
RLED
VDD33
VDD
OUTN
IN1
IN2
OUTH
LED
EN
C1
µC
EN
PD
OUT
GND
GND
OUT
GND
Figure 4: Principle of controlled light barrier application using a micro-controller
The photo diode current is compared to two threshold levels. The result OUTH from the higher comparison level may be used to detect the
light reserve.
Evaluation of a single light pulse
The photodiode is operated against ground and is reverse biased at a constant voltage of 1.2V. The input impedance of pin PD is kept low
(<1 kOhm @ 100kHz) in order to minimize the influence of the parasitic capacitance of the photodiode. To ensure proper operation under high
ambient-light conditions, the photo diode DC current can be up to 2 mA.
The resulting current from the light pulses are converted to a voltage, filtered, amplified and compared to two different threshold levels. The
lower threshold SENSN (input related 60nA typical) is used for the detection of the signal, the higher threshold SENSH (input related to
96nA typical) is used to provide an output when a certain signal reserve is achieved.
To detect the received light pulse properly, the given threshold must be at least five times higher than the rms value of the noise floor
generated by the circuitry without AC light stimulation.
The comparator results are digitally filtered and output at pin OUT and OUTH.
The parameter TPER defines the scan period in the standalone light barrier application but has also an impact to the settling time of the
receiver in the controlled mode application. It this case it has to be set corresponding to the scan period. Refer to the description of the TPER
command.
For each single light pulse, received and detected by the photodiode, the threshold levels for output OUTN and for output OUTH can be set by
programming (parameter SENSN resp. SENSH). They are processed according to the following principle to propagate the output signals
OUTN and OUTH resp. OUTNINT and OUTHINT. As far the received light pulse signal exceeds the corresponding threshold level, the pulse will
be recognized as a valid pulse and the detection circuit sets the appropriate output signal OUTN INT or OUTHINT
.
IPD
Light pulse detection
IPD
Light reserve detection
Threshold levels:
Light reserve OUTH
Signal output OUTN
t
t
t
t
t
t
OUTNINT
OUTHINT
Figure 5: Pulse evaluation
© 2011 ESPROS Photonics Corporation
Characteristics subject to change without notice
7
Datasheet epc110 - V2.1
www.espros.ch
EPC [ ESPROS PHOTONICS CORP ]
