cable, carrying nearly an amp of current on each twisted pair in
the latest spec, while still allowing for 10GBASE-T data transfer.
While an impressive spec, users will need to be cognizant of
potential heat effects taking advantage of this new capability.
Circuit Protection
So how does one protect vital equipment from power spikes
without interfering with the communications that allow these
devices to work properly? This might seem like a challenge to
system designers who are very good in their particular areas, but
would rather not be bothered with—and might even consider
neglecting—such important protections. The good news is that
Bourns already has multiple reference designs ready to fulfill this
role in the form of their PortNote
®
solutions.
Their first PoE reference design is meant for 10/100 Base-T
Powered Devices (PD) and provides both ESD and overcurrent
protection. This reference design includes a Transient Voltage
Suppression (TVS) diode array, a pair of bridge rectifiers, a single
TVS diode, and a transformer. Bourns also provides a design that
protects PSE, including the same TVS diode array and transformer
as the PD solution, but adds a resettable fuse, and does not use a
single diode or bridge rectifier as in the other design.
On a slightly different note, Bourns does have a solution ready
for traditional Ethernet connections where ESD is a threat.
While somewhat out of the scope of this article, it could be a
good design to consider for other wired Ethernet applications.
Whatever solution is expedient for an application, these PortNote
designs give an excellent starting point for Ethernet protection.
Once properly integrated into either a PD, PSE, or traditional
wired Ethernet device, this will make for a seamless installation
that end users never have to think about.
While PoE will initially work with or without this kind of circuit
protection, it's important to think about how things could go
wrong once installed, and the expense and potential reputation
damage when dealing with returns. As PoE usage increases,
especially in rugged industrial, automotive, and security
applications, designing a hardened product that is as, if not
more, reliable than using AC "mains" power will be essential
going forward.
| 16 |
Digi
®
XBee
™
Cellular LTE Cat 1
Digi
®
XBee
™
Cellular LTE Cat 1
MULTIFUSE
®
PPTC RESETTABLE FUSES
BMS ISOLATION TRANSFORMERS
• The space-saving freeXpansion
™
process enables smaller surface mount
package sizes
• Multifuse
®
devices handle larger currents
and voltages with improved resistance
stability
• PPTC resettable fuses provide
continuous circuit protection
until a fault is removed
• Support serial daisy chain/IsoSPI
• include common mode chokes
for noise rejection for BMS
applications
• Hi-Pot Isolation Voltage:
4300VDC
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