Page 2.2
32-CHANNEL DIGITAL I/O MODULE 40-412
pickering
SECTION 2 - TECHNICAL DESCRIPTION
GUIDANCE ON USING THE 40-412
Output Drivers
The 40-412 provides two output driver types on each of the 32 channels:
•
High Side Driver.
The high side driver allows the user to set the output voltage actively high to an externally
supplied voltage source. The external voltage source can be b5V and +50V relative to ground.
•
Low side driver.
The low side driver actively connects the output to ground.
The software driver inhibits both the high and low side drivers being turned on at the same time.
Each driver output is fully protected from thermal, voltage or current overloads. However, continuous operation at
voltages beyond the stated ratings may cause damage.
Each driver contains overvoltage protection that can be used to protect the driver from inductive back EMF spikes
generated when turning coil currents off. Using this protection to manage the back EMF will not cause damage to
the driver, however the sudden current change can generate EMC events. Pickering Interfaces recommends that
where ossi le the user should rovision local measures such as a wheel diode to limit the ack
current
ow through the ca les
he user can select oth drivers to e inactive to rovide a tri state o en out ut voltage
The external voltage source needs to be applied only if the high side driver is required to be used, it can grounded
or left unconnected if the high side driver is not required to be used.
Driving Inductive Loads
Users can use the high/low side drivers to drive highly inductive loads such as the coils of relays or solenoids, the
protection circuits in the 40-412 will ensure the drivers are not easily damaged. However, it is recommended that
precautions are taken to manage the resulting EMC issues that might arise.
High Side
Driver
Vext
FP_GND
En
40-412
GND
D1
D3
D2
Output
External Voltage
Figure 2.2 - Using the 40-412: Driving an inductive load with a High Side Driver
When using the high side driver, on driver closure, current will build in the coil until it reaches a steady state. When
the driver is opened, the energy in the inductor will need to be discharged. This discharge can be through the diode
inside the
igure
this will not damage the
owever the discharge ma cause a ground
s ike that ma result in
emission e recommend that where ossi le a local diode is fitted
igure
which will reduce the ground current owing and reduce the
emissions
