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Input / Output 4-9MN1928
4.4.2.2 DOUT8 - DOUT11
Outputs DOUT8 - DOUT11 are driven by a ULN2003 device. The outputs are designed to sink
current from an external supply (typically 24VDC), but have no overcurrent or short circuit
protection. When an output is activated, it is grounded through the ULN2003.
The ULN2003 has a maximum power dissipation of 900mW at 25°C. The total output
requirements of DOUT8 - DOUT1 1 m ust not exceed this limit. The maximum current limit for
an individual output is 400mA if only one output is in use, reducing to 50mA if all outputs are in
use. These limits are for a 100% duty cycle.
DOUT8 - DOUT11 are sourced from the same ULN2003 device as the DIR2 and STEP2
outputs (see section 4.5.1), so the current demands of these signals must also be considered.
If an output is driving an inductive load such as a relay, a suitably rated diode must be fitted
across the relay coil, observing the correct polarity. This is to protect the output from the
back-EMF generated by the relay coil when it is de-energized.
DOUT8
NextMove ES
ULN2003
MintMT
OUTX.8
74AHCT244
DGND
GND
Load
supply
24V
Load
supply
GND
a13
a3
Output Load
(Relay with
diode shown)
Figure 9 - Digital outputs (DOUT8-11) - DOUT8 shown