The LE87271EQCT is a single-circuit line driver designed for XDSL customer-premises equipment (CPE) — the modem or gateway on the subscriber side of the DSL link. Its function is to amplify the analog signal from the DSL transceiver onto the twisted-pair line, driving the line impedance with enough voltage swing and current to meet the loop-length and data-rate targets. The part operates from a 12.6 V to 15.4 V supply rail, drawing 26.1 mA typical supply current. That 1.37 W power dissipation budget means the exposed pad on the 20-VFQFN package must be soldered to a copper plane on the PCB to keep the junction temperature within the -40°C to 125°C operating range.
Supply rail and thermal design notes
The supply voltage tolerance is tighter than many general-purpose op-amps: 12.6 V to 15.4 V, so the rail needs a regulated supply — a 12 V rail from a DC-DC converter will be too low, and an unregulated wall-wart will drift out of spec under load. Budget a linear regulator or a tight-output DC-DC set to 13.5 V nominal. The 1.37 W power dissipation at 26.1 mA supply current is the thermal design ceiling. The 20-VFQFN package with exposed pad (4x4 mm) relies on the PCB copper pour to sink heat.