Dual input, 2.5A step-down DC/DC achieves 95% efficiency

October 06, 2016 // By Graham Prophet
LTC3126 is a 2.5A, 2.4V to 42V input, synchronous step-down switching regulator with integrated dual input PowerPath control. Its power stage topology enables operation from either of two independent power sources, with seamless, internally controlled transitions between inputs to ensure a stable output voltage during hot-plug and power source disconnect events.

Internal power switches and synchronous rectification combine to deliver 95% efficiency (achieved at at 1A, VIN = 12V, VOUT = 5V) over a wide voltage range, enable a fast transient response and ensure loop stability while switching at 2 MHz. Operation over 200 kHz to 2.2 MHz, fixed frequency PWM, allows designers to avoid critical noise-sensitive frequency bands such as AM radio, while providing a compact solution footprint.

The LTC3126’s current mode topology with 60 nsec minimum on-time is internally compensated, eliminating the need for external compensation components. Burst Mode operation maintains high efficiency at low output currents while keeping peak-to-peak output ripple below 1%. It features a quiescent current under 2 µA in no-load standby conditions, for always-on systems and portable applications. The device’s 2.4V to 42V input and 0.818V to VIN output voltage ranges are suited for automotive applications. Other key applications include portable industrial/communications test equipment, battery and supercapacitor backup power systems, automotive power with battery backup, uninterruptible power supplies, and systems powered by unregulated wall adapters or single to multicell stacks of most battery chemistries.

The LTC3126’s integrated lossless PowerPath circuitry supports seamless operation from two separate input power sources. Pin-selectable ideal diode-OR and priority input modes with user-programmable undervoltage lockout thresholds provide full control over the transition between the input power sources. The fast, automatic switchover provided by this internal PowerPath eliminates the need for hold-up capacitors and minimizes disturbances on the output rail. An active input channel indicator and independent input and output power-good signals provide complete feedback of the power system status. Other features include 1 µA current in shutdown, internal soft-start and thermal protection.

In thermally enhanced 28-lead TSSOP and 4mm x 5mm QFN packages, pricing starts at $6.25 (1000).

Linear Technology: www.linear.com