The ADI 72V hybrid step-down DC/DC controller reduces the size of the solution by 50% compared to traditional architectures

     Analog Devices announced the LTC7821 from Power by Linear, the industry's first hybrid step-down synchronous controller, which combines a switching capacitor circuit with a step-down synchronous controller. Reduces the size of DC/DC converter solutions by up to 50% compared to traditional buck solutions. This improvement was achieved by tripling the switching frequency (without sacrificing efficiency). Alternatively, solutions based on the LTC7821 can provide efficiency gains of up to 3% when operating at the same frequency. Other benefits of the LTC7821 include low EMI and reduced MOSFET stress due to the soft-switching front end, making it ideal for power distribution, data communications and telecommunications, and next-generation non-isolated intermediate bus applications in emerging 48V automotive applications.

     The LTC7821 operates in the input voltage range from 10V to 72V (80V absolute maximum) and can produce output voltages from 0.9V to 33.5V and currents of tens of amps, depending on the selection of external components. In typical 48V to 12V/20A applications, 97% efficiency is achieved when the LTC7821's switching frequency is 500kHz. Conventional synchronous buck converters can achieve the same efficiency only by performing switching operations at 1/3 of the operating frequency, resulting in the need for much larger magnetic components and output filter components. The external MOSFETs perform switching operations at a fixed frequency and can be set from 200kHz to 1.5MHz.

     The LTC7821's powerful 1ΩN channel MOSFET gate driver maximizes efficiency and is capable of driving multiple MOSFETs in parallel to meet the requirements of higher power applications. Because of the LTC7821's current-mode control architecture, multiple LTC7821s can operate in a parallel, multiphase configuration, leveraging their superior current-sharing capabilities for much higher power applications.

     The LTC7821 implements a number of proprietary protection features for rugged performance in a wide range of applications. The LTC7821-based design eliminates the surge current typically caused by switching capacitor circuits by pre-balancing the capacitor during startup. In addition, the LTC7821 monitors system voltage, current, and temperature to detect faults and uses a detection resistor to provide overcurrent protection. When a certain FAULT situation occurs, the device stops the switch operation and pulls the /FAULT pin to a low level. A built-in timer can be set for the appropriate restart/retry time. The EXTVCC pin enables the LTC7821 to rely on the lower voltage output of the converter or other available power supply up to 40V, reducing power consumption and improving efficiency.