Provides continuous power when input power is interrupted

Linear Technology Korea announced the release of the LTC3643, a bidirectional high-voltage boost capacitor charger that automatically switches to a buck regulator suitable for system backup. Linear stated that the single-inductor topology, featuring built-in PowerPath™ functionality, operates two separate switching regulators, reducing size, cost, and complexity, and operates in two modes: boost charging mode and buck backup mode. The charging mode efficiently charges an array of electrolytic capacitors up to 40V using an internal switch with a 2A current from an input voltage between 3V and 17V.

In backup mode, when the input power drops below the PFI (programmable power-fail) threshold, the step-up charger conversely operates as a synchronous step-down regulator, maintaining power from the backup capacitor to the system rail for a certain period of time. During the backup period, the current limit can be programmed from 2A to 4A. This device is suitable for high-energy, relatively short-backup-period backup capacitor systems, power failure backup systems, solid-state drives (SSDs), and battery stack charging applications.

When charging the backup capacitor, the LTC3643 can use a low-value external sense resistor to prioritize power to the system load while maintaining precise current limits from the input power source. The input current limit can be programmed with a 50mV threshold for the current sense resistor, preventing the system power source from reducing the capacitor charging current. The step-down converter operates at a frequency of 1 MH and minimizes external component size. Low standby current Burst Mode® operation during regulation maximizes energy utilization from the backup capacitor.

The LTC3643 provides ideal diode operation from the input power supply by providing a gate drive signal to an external PMOS switch. This product enables efficient power transfer while providing complete isolation between the input power supply and the system load during backup mode. Other features include an integrated N-channel MOSFET for output/CAP cutoff, ±1% reference precision for system voltage regulation, and charge state and input power fault outputs.

The LTC3643 is housed in a compact, thermally enhanced 24-pin 3mm x 5mm QFN package and operates in E- and I-grades over a temperature range of –40°C to 125°C. The E-grade device is priced at $4.45 per unit in 1,000-unit quantities. All grades are available immediately.