SLOA327 November 2022 LM25017 , LM25018 , LM25019 , LM25180 , LM25183 , LM25184 , LM5017 , LM5018 , LM5019 , LM5160 , LM5160A , LM5161 , LM5168-Q1 , LM5169-Q1 , LM5180 , LM5181 , SN6501 , SN6505A , SN6505B , SN6505D-Q1 , SN6507 , TPS55010
Designers of programmable logic controller (PLC) I/O modules or other industrial low-power applications have to find a reliable design for proper and safe operation of their designed circuits under the conditions of a harsh industrial environment. Isolated power converters are frequently found in such applications and help in the following:
Common design requirements for such isolated power converters used specifically in PLC I/O module applications include the following, which are also similarly applicable to other industrial low-power applications:
Table 1-1 provides an overview of usable isolated power topologies and proposed TI devices addressing the aforementioned requirements.
All of the listed topologies are optocoupler-less approaches – although the underlying traditional topologies which are found in higher power designs are known to use optocoupler feedback.
The table groups the proposed topologies into the following categories:
The provided minimum and maximum input voltage values (VIN minimum, VIN maximum) of the devices represent the best-case values of all the listed devices supporting a specific topology. The 2.95 V given as VIN minimum for the fly-buck topology is related to the minimum VIN of the TPS55010, whereas the 120 V given as VIN maximum for this topology represents the maximum VIN of the LM5168 and LM5169. Specific topologies like fly-buck-boost and primary side regulated flyback(3) require an additional margin to be applied.
The given maximum output power (maximum POUT) is representing the capability of the most powerful device given for a specific topology and depends furthermore on the ratio VOUT/VIN and the turns ratio of the used transformer.
V_ISO stands for the isolation voltage of the used transformer and is often related to specific technical standards.