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BusWorks® Model 989EN U
ser’s Manual Modbus TCP/IP Digital I/O & Counters
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Acromag, Inc. Tel:248-295-0880 Fax:248-624-9234 Email:
13
EXT
EXC
8 to 28V
EXC
ON
RTN
I/O
OFF
V
5.5V MIN
EXCITATION IS REQUIRED. EXTERNAL EXCITATION IS 8V MIN TO 31V MAX.
OPEN-DRAIN OUTPUTS SHARE RETURN.
AVOID ENABLING FAST SHORT FAULT PROTECTION WITH INCANDESCENT LAMPS TO
AVOID NUISANCE TRIPS WITH RESULTANT HIGH INRUSH CURRENTS.
INCANDESCENT LAMP CONTROL
Other Considerations For Output Control
•
Built-in protection in the outputs will automatically shut-down specific
output operation for current-limit, thermal overload, excitation over-
voltage, and output drain over-voltage conditions. The outputs can
optionally be programmed to automatically retry their control, or
remain OFF following a thermal or over-voltage shut-down (default
response).
•
If you enable open-load detection, a 50uA pull-down current will be
present with the output in the OFF state. This opposes the input
wetting current pull-up, so inputs must be tri-stated for this to work.
You may wish to reconsider enabling this detection if you happen to
be driving loads sensitive to small currents, or you cannot tolerate
unused inputs being pulled to the ON state.
You can select a faster responding 100-450us shutdown mechanism that is
triggered based on output Vds measurement (default), as opposed to a
thermal shutdown which allows the output to heat-up. Normally if an output
drives a shorted load, built-in thermal protection will kick-in to protect the
output. This effectively allows output port protection to be tailored to
incandescent lamp loads (thermal), or inductive loads (faster). However, the
fast shutdown may not trigger the thermal fault flag, as it acts too fast to
capture. But fast action does limit repeated thermal stresses which helps
preserve the life of the output driver.
CONNECTIONS
Digital Outputs
Incandescent Lamp Control
To drive lamps, you may avoid
using the fast short-fault
protection mode as it might
cause nuisance shut-downs as
a result of high ON inrush
currents.
Although selecting fast
shutdown helps limit repeated
thermal stress on the output
driver, it acts too fast to report
it via the output fault flags.