epc700/epc702
Programming
The time delay (t
del
), until the output is turned off after the detection of an over-current condition can be programmed in order to adapt the ti-
ming to specific requirements, i.e., if a capacitive load has to be operated or an external transistor allows other values. The default value is
50μs which allows to charge a load capacitor of approx. 100 – 500nF without an external power transistor, dependent on the source impe -
dance, the load impedance and the voltage V
L
.
The time until the output is turned on again after a short circuit can be programmed as well (t
minOFF
). This “self-healing” mechanism is very use-
ful because no operator interaction is necessary after a short circuit to enable normal function once the short circuit has been eliminated. The
default value is 500ms which means that the device tries to turn the output on after 0.5s waiting time in the short circuit mode. This waiting
time is recommended as long as t
del
is not changed. If t
del
has been changed, the parameter t
minOFF
shall be changed accordingly in order to
respect parameter f
rt
. The user has to ensure that the maximum operation conditions never exceed in order to avoid damage of the device.
It is to note that the parameters programmed are stored in a non-volatile random access memory. Thus, the parameters can be lost after a
power down for longer than 5ms (data retention time @ 25ºC: min. 100ms). The corresponding requirements for safety applications have to
take in consideration. Parameters can be changed as many times as necessary and even under operation to change the behavior of an
output. During power-on, the default values are restored automatically.
Programming Interface
The interface to store changed parameters are the pins IN and STATUS. IN is the chip select pin and STATUS, which is under normal opera -
tion an output, is used as an input pin. As long as the IN pin is at low state, parameters can be stored through the STATUS pin. Since IN is low
during the programming of new parameters, OUT is low as well.
The digital input high threshold is typically at 2.2V, thus a 5V compatible communication. Please note that the voltage at STATUS should not
exceed 5.5V.
Single Wire Communication Interface
The epc70x is based on a single wire communication interface by using the STATUS pin. Programming is done by a 21-Bit Manchester code
according to IEEE 802.4.
Clock
(internal)
Data
Manchester
code
1
0
0
1
1
0 0
Figure 8: Manchester encoding sample
data-stream. Each positive clock-edge in the Manchester encoded data (indicated with the up-arrow) corresponds to a 1 and each negative
clock-edge (indicated with the down-arrow) corresponds to a 0.
Data Clock Frequency Range
The communication frequency range has to be according to Table 1.
minimal
Data clock
396kHz
typical
450kHz
maximum
540kHz
Table 1: Frequency range for programming
Configuration Bit Stream for changing the delay time
In order to guarantee a reliable communication with the Manchester encoded bit stream on STATUS, some additional bits have been added to
the configuration bits. Table 2 shows the digital pattern for the delay time configuration and the recovery time configuration.
Bit #
t
Del
Value
T
minOFF
Value
0
1
1
1
0
0
2
1
1
3
1
1
4
0
0
5
0
0
6
0
0
7
0
0
8
0
1
9
1
0
10
1
0
11
1
0
12
1
1
13
0
0
14
D1
O1
15
D2
O2
16
D3
O3
17
1
1
18
d1
o1
19
d2
o2
20
d3
o3
Table 2: Configuration of the delay and the recovery time
© 2011 ESPROS Photonics Corporation
Characteristics subject to change without notice
7
Datasheet epc700_702 - V2.2
www.espros.ch
EPC [ ESPROS PHOTONICS CORP ]
