Operation For Overload Or Short Circuit; Load Short-Circuit Protection And Line Disconnection Detection For Basic I/O Units; Load Short-Circuit Protection And Line Disconnection Detection For Cj1W-Od202 - Omron CJ2 CPU UNIT User Manual

A-6 Load Short-circuit Protection and
Line Disconnection Detection for
Basic I/O Units
A-6-1 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 out-
put current (Iout) will flow.
Normal Operation
ON
OUT
OFF
ON
I
OUT
OFF
ON
ERR
OFF
If the output (Iout) is overloaded or short-circuited exceeding the detection current (Ilim), the output cur-
rent (Iout) will be limited as shown in figure below. When the junction temperature (Tj) of the output tran-
sistor 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 temperature (Tj) of the transistor drops down to the reset temperature (Tr), the ERR indica-
tor will be automatically reset and the output current will start flowing.

Operation for Overload or Short Circuit

ON
OUT
OFF
I
lim
ON
I
OUT
OFF
ON
ERR
OFF
If the line is disconnected and the output current (Iout) drops below the line disconnection detection cur-
rent (IOL), the ERR indicator will light as shown in the following figure.
Operation for Disconnected Line with Output Current below the Line Disconnection Detection Current
ON
OUT
OFF
ON
I
OUT
OFF
ON
ERR
OFF
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.
CJ2 CPU Unit Hardware User's Manual
Tj =Tstd Tj =Tr
I
OL
A B C
OUT: OUTPUT instruction
I : Output current
OUT
ERR: Alarm output, ERR indicator
I : Short-circuit detection current
lim
I : Disconnection detection current
OL
T : Junction temperature of transistor
j
T : Thermal shutdown temperature
std
T : Reset temperature
r
Appendices
A-149