Omron CJ - 09-2009 Operation Manual page 636

Specifications of Basic I/O Units
Load Short-circuit Protection and Line Disconnection Detection for
CJ1W-OD202
This section describes the load short-circuit protection of the CJ1W-OD202 Output Units.
As shown below, normally when the output bit turns ON (OUT), the transistor will turn ON and then output cur-
rent (Iout) will flow. If the output (Iout) is overloaded or short-circuited exceeding the detection current (Ilim), the
output current (Iout) will be limited as shown in Figure 2 below. When the junction temperature (Tj) of the output
transistor reaches the thermal shutdown temperature (Tstd), the output will turn OFF to protect the transistor
from being damaged, and the alarm output bit will turn ON to light the ERR indicator. When the junction tem-
perature (Tj) of the transistor drops down to the reset temperature (Tr), the ERR indicator will be automatically
reset and the output current will start flowing.
Figure 1: Normal Condition
Figure 2: Overload or Short-circuit
Line Disconnection
If the line is disconnected and the output current (Iout) drops below the line disconnection detection current
(I ), the ERR indicator will light as shown in Figure 3.
OL
Figure 3: Line Disconnections
O N
O U T
O FF
O N
I
O U T
O FF
O N
ER R
O FF
588
I
O L
A B C
OUT: OUTPUT instruction
I : Output current
OUT
ERR: Alarm output, ERR indicator
I : Detection current
lim
Tj: Junction temperature of transistor
Tstd: Thermal shutdown temperature
Tr: Reset temperature
A: Load not connected or load line broken.
B: Current to load at or below line disconnection
detection current.
C: Rise of current to load too slow and error
detected before the disconnection detection
current was reached.
When load L is connected, the ERR indicator
may light and the Alarm Output Bit may turn ON
for approximately 100 ms. The programming
example given later in this section can be used
so that an error is not detected in this case.
Appendix A