Specifications

PL 3120/PL 3150/PL 3170 Power Line Smart Transceiver Data Book 169
Off-the-Shelf Switching Supplies
Most commercially available switching power supplies have been designed with some level of input noise filtering.
Frequently this level of filtering is adequate if the supply’s fundamental switching frequency falls within the
recommended ranges of Table 5.8 under all conditions.
Most off-the-shelf switching power supplies have a very low input impedance and require the addition of an input
inductor as described on the following page in the section titled Power supply-Induced Attenuation.
Full Custom Switching Supplies
Developing a custom switching supply, even one which employs a commercially available controller chip, is very
challenging and is only recommended if none of the other options outlined in this chapter are suitable. If this option
is chosen, it is recommended that it only be pursued by experienced switching supply and electromagnetic
compatibility experts. Even if such personnel are available, extra time must be allowed for design iterations during
development. If this approach is chosen, it is absolutely essential that the supply is verified to meet the input and
output noise masks provided later in this chapter.
Many of the off-line switching regulators available from Power Integrations Inc. (for example,
LinkSwitch
®
and TinySwitch
®
regulators) operate at frequencies which are not within the recommended
range for use with PL Smart Transceivers and thus they are not recommended for use with PL Smart
Transceivers. The TopSwitch
®
family of off-line switching regulators from Power Integrations operate within
the recommended range of frequencies at room temperature but they do not stay within the recommended
range over temperature. TopSwitch
®
regulators are therefore no longer recommended for powering PL Smart
Transceiver-based devices.
.
Most 1st and 2nd generation SIMPLE SWITCHER
®
regulators from National Semiconductor Corporation
operate at frequencies which are not within the recommended range for use with the PL Smart Transceivers
(that is, most LM25xx parts). Use of any SIMPLE SWITCHER regulator with a nominal operating frequency
of 52kHz, 100kHz or 150kHz is not recommended because these devices have a very wide frequency tolerance
which could result in operation outside the recommend range.
Newer SIMPLE SWITCHER regulators, for example LM26xx parts, with operating frequencies of ≥200kHz can be
used, however, a supply designed with one of these parts must still be verified to meet the noise mask requirements
of this chapter over all operating conditions.
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