Switching Regulator Has Burst-Mode Operation

Linear Technology has announced the LT3990, a 350mA, 60V ultralow quiescent current step-down switching regulator. Its burst-mode operation keeps quiescent current under 2.5uA in no-load condition. The LT3990's 4.3 to 60V input-voltage range makes it suitable for automotive and industrial applications that need continuous output with ultra-low power drain. Its internal 550mA switch can deliver up to 350mA of continuous output current at voltages as low as 1.21V.

The LT3990's burst-mode operation provides ultra-low quiescent current, suited for automotive or industrial systems that demand always-on operation and optimum battery life. Switching frequency is user programmable from 200kHz to 2.2MHz, enabling the designer to optimise efficiency while avoiding critical noise-sensitive frequency bands. The combination of its 10-lead 3 x 2mm DFN-10 (or MSOP) package and high switching frequency keeps external inductors and capacitors small, providing a very compact, thermally efficient footprint. The LT3990 utilises a high-efficiency 550mA, 300mV switch - with the necessary boost and catch Schottky diodes, oscillator, control and logic circuitry integrated into a single die.

Low ripple burst-mode operation ensures high efficiency at low-output currents while keeping output ripple below 5mVPK-PK. Design techniques and a high-voltage process enable high efficiency over a wide input-voltage range, and the LT3990's current-mode topology enables fast transient response and loop stability. Other features include a power-good flag, soft-start capability and output-short protection.

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