Echelon FT 3150 Smart Transceiver User Manual
Page 100
Chapter 4 - Hardware Design Considerations
94
FT 3120 / FT 3150 Smart Transceiver Data Book
Table 4.1 FT Smart Transceiver External Components
In Figure 4.1, capacitors C3 and C4 are used to provide DC voltage isolation for the FT Smart Transceiver when it is
used on a link power network or in the event of a DC power fault on the network wires. The capacitors are required to
meet L
ON
M
ARK
interoperability guidelines for the TP/FT-10 channel. These capacitors are not needed on devices that
will be connected exclusively to non-link power networks and do not require protection against DC faults. Two polar
capacitors are used to protect against the application of a DC voltage of either polarity, while providing a total
capacitance of 11µF. Alternatively, a single non-polar capacitor of 10µF may be used in either of the two legs which
connect to the network. The initial tolerance of the capacitor should be ±20% or less, and degradation due to aging
and temperature effects should not exceed 20% of the initial minimum value
Capacitors C5 and C6 are required on all new designs. They ensure that the FT Smart Transceivers support
EN61000-4-6 Level 3. Note that unlike the FTT-10A transceiver, the common mode noise immunity of the FT Smart
Transceivers is not significantly improved by the addition of the common mode choke specified in the L
ON
W
ORKS
FTT-10A Free Topology Transceiver User’s Guide.
Figure 4.2 shows an example implementation of the optional COMM_ACTIVE LED drive circuit block that is
referred to in figure 4.1 on the previous page.
Name
Value
Comments
C1
0.1µF for +5VDC decoupling
V
CC
decoupling capacitor for ESD protection
diodes D1-D2
VR1
470V MOV, 5mm, 40pF (typ.)
Panasonic ERZV05D471, Digi-Key P7186-
ND or equivalent.
C3, C4
22µF,
≥
50V, polar
DC blocking capacitors; see text
C5, C6
56pF, 5%, NPO or COG
To enable EN61000-4-6 Level 3
D1, D2
BAV99, 1N414-equivalent
ESD Transient clamping diodes
D3, D4, D5, D6
BAV99, 1N4148-equivalent
1N4934, 1N4935, FR1D, RS1D,
RS1DB
Differential network clamping diodes:
For up to 2kV Surge Protection
For up to 6kV Surge Protection