The power architecture in telecom systems uses a 48-V nominal input within a range from 36 to 75 V (European Telecom Standard Input range is 36 to 60 V). This input voltage to the card needs to be distributed to the point-of-load (POL) in the most electrically efficient, space-efficient, and cost-effective way possible. One method of power distribution involves bringing the 48-V input down to a 3.3-V board-level bus, then supplying the 3.3-V feed to the loads that required it, converting the other required voltages through several POL converters. Another scheme, more suitable for higher power boards, was to convert the 48 V to a 12-V board-level bus. The 12 V were not fed to any load directly, but would be converted to the needed voltage at the POL.
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