Power Supply Bypassing and Grounding
The PLT-22 transceiver requires the connection of external bypass capacitors. The
bypass capacitors should be placed as close as possible to the PLT-22 transceiver,
and low-impedance ground and supply traces should be used between the PLT-22
transceiver and the bypass capacitors. In addition to the bypass capacitors specified
for the Neuron Chip (see
Neuron Chip Data Book
2,3,18
), the recommended values of
the V
DD5
and V
A
bypass capacitors are, as follows:
V
DD5
:
None required if the V
DD5
supply at the PLT-22 transceiver pin 9
meets the noise masks described in Chapter 5. It is recommended
that PCB designs initially incorporate a 10µF 10V tantalum capacitor
and a 0.1µF ceramic capacitor on the V
DD5
suppy. These capacitors
can be eliminated if the design meets the noise masks in Chapter 5
and passes the receive performance tests described in Chapter 7
without the capacitors installed.
V
A
:
120µF (minimum) 16V, low-ESR (<0.3
Ω
@ 100kHz), high-frequency
aluminum electrolytic capacitor. Low ESR is required in order to
minimize V
A
ripple voltage when the transceiver drives low
impedance loads, drawing several hundred milli-Amperes of peak-to-
peak ripple current. Note that the V
A
bypass capacitor is an integral
part of the mains surge protection circuitry described in Chapter 4.
In particular, the coupling circuits of Chapter 4 require the use of an
aluminum electrolytic
type capacitor with a voltage rating of
16V
.
Higher or lower voltage ratings will likely result in surge immunity
which is significantly below the verified levels documented in
Chapter 4.
The PLT-22 transceiver provides three ground pins. For proper operation,
all three pins must be connected to ground with low-impedance traces, or
to a ground plane between the transceiver and the Neuron Chip.
Band-In-Use (BIU) and Packet Detect (PKD) LED Connections
The PLT-22 transceiver supplies two output signals, PKD and BIU, that are
intended to drive low-current light-emitting diodes (LEDs). Both signals are active-
high and must be connected to separate LEDs, with series current-limiting resistors
added between the LEDs and ground.
A Band-In-Use detector, as defined under CENELEC EN 50065-1, must be active
whenever a signal that exceeds 80dBµVrms anywhere in the frequency range
131.5kHz to 133.5kHz is present for at least 4ms. The Band-In-Use detector is
defined by CENELEC EN 50065-1 as part of the CENELEC access protocol. The
PLT-22 transceiver incorporates the CENELEC access protocol, and the PLT-22
transceiver may be programmed to enable or disable its operation. (See
CENELEC
Access Protocol
in Chapter 3 for more information.) When the PLT-22 transceiver is
programmed such that the CENELEC access protocol is enabled, the BIU signal is
active high whenever the CENELEC-defined conditions for Band-In-Use are met.
When the transceiver is programmed such that the CENELEC access protocol is
L
ON
W
ORKS
PLT-22 Transceiver User’s Guide
2-7
Summary of Contents for LONWORKS PLT-22
Page 6: ...iv Echelon...
Page 14: ...1 8 Introduction...
Page 67: ...LONWORKS PLT 22 Transceiver s User Guide 5 7 Figure 5 3 Capacitor Input Power Supply Schematic...
Page 92: ...6 10 Design and Test for Electromagnetic Compatibility...
Page 110: ...7 18 Communication Performance Verification...
Page 114: ...8 4 References...
Page 118: ...A 4 Appendix A...
