Linear Technology Corporation introduced the LTC3643, a new bidirectional high-voltage step-up capacitor charger that automatically converts to a step-down regulator for system backup.
A proprietary single-inductor topology with integrated PowerPath functions does the work of two separate switching regulators, reducing size, cost, and complexity. The LTC3643 operates in two modes-boost charging mode and buck standby mode. The device's charge mode can effectively charge up to 40V electrolytic capacitor arrays with input power from 3V to 17V, and the internal switch is rated at 2A. In standby mode, when the input power drops below the programmable power failure (PFI) threshold, the boost charger operates in reverse as a synchronous buck regulator to power and maintain system power through a backup capacitor. During backup, the current limit can be set to 2A to 4A, making the device ideal for high-energy, relatively short-lived backup capacitor systems, power failure backup systems,
When charging the backup capacitor, the LTC3643 can use an external low-value sense resistor to maintain accurate current limit from the input power source while prioritizing power to the system load. The input current limit can be programmed with a 50mV threshold across the current-sense resistor to prevent system power by reducing capacitor charging current. The step-down converter operates at 1MHz, minimizing the size of external components. Low Quiescent Current Burst Mode® operation during regulation maximizes the energy consumption of the backup capacitor. The LTC3643 provides ideal diode operation on the input power supply by supplying the gate drive signal to an external PMOS switch. This enables efficient power transfer while providing full isolation between input power and system load in standby mode.
The LTC3643 is housed in a compact, thermally enhanced 24-lead 3mm x 5mm QFN package with Class E and Class I operation from -40C to 125C. The company says all products are available from stock.
