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Supercapacitor Backup Power Supply for E-Meters Reference Design

The PMP30528 reference design from Texas Instruments automatically provides back-up voltages to an E-Meter during a power interruption. While the input voltage is between 10V to 12V, two buck controllers (TPS62147, TPS62173) generate 3.9V at 2A and 5V at 150mA. An optional synchronous boost generates 3.3V at 50mA.

A discrete charge circuit charges a supercapacitor with a constant current up to an adjustable voltage of 2.7V. When the input voltage fails, a synchronous boost takes over and boosts the supercap voltage to 3.9V.

The supercap capacitance and voltage defines the energy, which is available for the backup. The design enables a stable backup output of 3.9V at 200mA for about 70s until the output voltage drops.

Features

  • Seamless transition between mains power and back-up operation
  • Designed to support high output power RF communications such as LTE, NB-IOT, or wireless MBUS or 6LoWPAN
  • Single supercapacitor design to minimize system cost
  • Discrete constant current supercapacitor charger
  • Complete tested design with available design files and test report

PMP30528 schematic (click on schematic to enlarge)

Available design files include: PMP30528 Gerber, PMP30528 CAD Files, PMP30528 PCB, PMP30528 Assembly Drawing, PMP30528 BOM, and PMP30528 Schematic.