An article from Texas Instruments discusses the use of isolated 3.3 to 5V converters in long distance data-transmission networks. The article states that although isolated DC/DC converter modules for 3.3 to 3.3V and 5 to 5V conversion are readily available on the market, 3.3 to 5V converters in integrated form are still hard to ﬁnd. Even if a search for the later proves successful, these speciﬁc converters— in particular, those with regulated outputs—often possess long lead times, are relatively expensive, and are usually limited to certain isolation voltages.
A low-cost alternative to integrated modules is a discrete design, if an application requires isolation voltages higher than 2kV, converter efﬁciency higher than 60%, or reliable availability of standard components. The drawback of designing a discrete DC/DC converter is that it requires a great deal of work: choosing a stable oscillator structure and break-before make circuit, selecting good MOSFETs that can be driven efﬁciently by standard logic gates, and performing temperature and long-term-reliability tests. This entire effort costs time and money. Therefore, before rushing into such a project, the designer should consider that integrated modules have usually passed temperature tests and have met other industrial qualiﬁcations. These modules not only represent the most reliable solution, but also provide a fast time to market. The see the entire article at Element14.