Synchronous step-down regulator delivers high efficiency with ultralow EMI/EMC emissions

Linear Technology has announced the LTC7103, a 2.3A, 105V input capable synchronous step-down switching regulator. Its wide 4.4V to 105V input voltage range is designed for operation from a continuously high voltage input source or from an input that has high voltage surges, eliminating the need for external surge suppression devices. This makes the device ideal for a variety of transportation, industrial and communications applications such as 48V automotive, 36V to 72V telecom, avionics and dual battery vehicle systems. The device’s high efficiency internal power switches can deliver up to 2.3A of continuous output current. The device incorporates proprietary technology that reduces EMI/EMC emissions to an ultralow level, easily passing automotive CISPR#25, Class 5 limits without sacrificing efficiency. It delivers efficiencies over 96% while regulating a 12V output and over 90% while regulating a 3.3V output. To avoid noise-sensitive frequency bands, the switching frequency can be set between 200kHz and 2MHz, or synchronized anywhere in this range using the device’s internal phase-locked loop. The device uses a unique constant frequency average current mode control architecture. This enables a fast transient response with excellent loop stability as well as fast and accurate output current programming and monitoring with no external sense resistor. This adjustable, brick-wall style current limit feature makes it well suited for current source applications such as battery or capacitor charging and LED lighting. The device draws only 2µA of input quiescent current while regulating the output voltage at no load, extending battery operating life in always-on applications. Low ripple Burst Mode operation maintains high efficiency at light load currents while keeping output ripple small. To further minimize ripple, a pulse-skipping mode can also be selected. The device features a low minimum on-time of 40ns and a maximum duty cycle of 100%, enabling the output voltage to be set anywhere from 1V up to the input voltage. It features eight pin-selectable fixed output voltage set points that include commonly used rails from 1.2V to 15V. These pre-programmed output voltages save board space and reduce the no-load quiescent current by eliminating an external resistor divider. Internal voltage loop compensation automatically adjusts based on the switching frequency to ensure both speed and stability. Alternatively, the voltage loop can be optimized externally using OPTI-LOOP compensation.