Dual Input Regulator Switches to Backup

March 17, 2015 | 01:37
Dual Input Regulator Switches to Backup
Dual Input Regulator Switches to Backup

Uninterruptable power supplies need a reliable switch over mechanism to ensure the output voltage remains continuous when the main power source goes down. The new LTC3118 regulator chip from Linear Technology is a synchronous buck-boost DC/DC converter which takes care of the switch over automatically and accepts two input power sources in the range of 2.2 V to 18 V.

The wide input voltage range allows either input to be either above, below or equal to the programmable output voltage. The current-mode converter uses a fixed 1.2 MHz switching frequency and can supply up to 2 A continuous output power.


Main features of the LTC3118 include:

  • Integrated high efficiency dual input PowerPath plus Buck-Boost DC/DC converter
  • Ideal diode or priority VIN select modes
  • VIN1 and VIN2 range: 2.2 V to 18 V
  • VOUT range: 2 V to 18 V
  • VIN can be above, below or equal to VOUT
  • Generates 5V at 2A for VIN > 6V
  • 1.2 MHz low noise fixed frequency operation
  • Current mode control
  • All internal N-Channel MOSFETs
  • Pin-selectable PWM or Burst Mode operation
  • Accurate, independent RUN pin thresholds
  • Up to 94% efficiency
  • VIN and VOUT power-good indicators
  • IQ of 50 μA in sleep, 2 μA in shutdown
  • 4 mm × 5 mm 24-lead QFN or 28-lead TSSOP packages


In a typical application the main input power may be provided by a wall adapter unit while the backup can be either batteries or supercaps.

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