Energy Storage Linear Supplies
For products requiring minimal application current and safety isolation, an
energy storage linear supply may be the smallest and most cost effective option.
Consider a node based on a Neuron 3120 Chip, operating at 2.5MHz and
consuming 1mA of application and I/O current. Using a linear power supply for
the V
A
supply and a linear regulator for the V
DD5
supply, the worst case current
requirements are presented in Table 5.2.
Table 5.2
Example Worst-Case Node Current Consumption
Transmit Receive
PLT-22 V
A
250mA 6mA
PLT-22 V
DD5
18mA 23mA
Neuron 3120 Chip
(@2.5MHz)
8mA 8mA
Application & I/O
Current
1mA 1mA
78L05 Regulator
Current
5mA 4mA
Total 282mA
42mA
A traditional linear supply would require a transformer with an output current
rating of
≥
300mA. By taking advantage of the PLT-22 transceiver’s power
management feature, an energy storage linear supply can be built with a 100mA
transformer.
Figure 5.4 shows an example of an energy storage linear supply. This example
supply meets the criteria listed in the energy storage section of this chapter.
With a transient load of 130mA for 90.7ms added to a constant 42mA receive
load, this supply does not droop below 11.4V. This supply also maintains
≥
9.0V
after a 250mA load is added to the constant 42mA load for 90.7ms. Both of these
criteria hold true even with an AC line voltage which is 10% low and an output
capacitance value that is 20% low. In addition, this example supply supports
duty cycles of
≥
50% under typical transmission conditions and
≥
10% over worst
case line voltage and component tolerances.
AC Line
Voltage
V
V
78L05
12.6 VAC @100 mA
4700 µF
16 V
±20%
14 V, 5W
±5%
IN5351B
+
A
DD5
(5V)
Figure 5.4
Energy Storage Linear Power Supply
Note that this supply is kept from exceeding the 16V maximum supply voltage
rating of the PLT-22 transceiver by the inclusion of zener diode over-voltage
protection. Without this diode, the combination of high AC line voltage and light
5-8
Power Supplies for the PLT-22 Transceiver
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...
