Compact 60V DC/DC buck converters for extra flexibility

7th December 2020

Alex Lynn

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The STMicroelectronics L7983 is a compact, three to 60V, 300mA synchronous DC/DC buck converter with flexible, dynamic-mode selection to satisfy noise-sensitive applications and maximise efficiency at light load.

Special ST innovations engineered into the L7983 allow control of the low-side power MOSFET to provide a low-noise mode (LNM) with constant switching frequency and an alternative low-consumption mode (LCM). In LCM, the converter maximises the efficiency while powering low or idle loads. The mode is selected using an external pin that can be controlled dynamically by the application or preset by tying high or low.

With its wide input-voltage range, the L7983 can operate from 12 and 24V industrial buses with a generous safety margin. It is also suited to battery-powered applications and can be used in industrial fail-safe systems, decentralised intelligent nodes, appliances, robotics, telecom equipment, and precision-sensing applications that leverage the easy-to-use low-noise mode.

While the high maximum input voltage ensures robust and reliable performance, the L7983 enhances design flexibility by allowing a wide switching-frequency range of 200kHz to 2MHz. In addition, optional spread-spectrum dithering helps minimise electromagnetic interference (EMI). Drawing quiescent current of 10µA, the converter has minimal impact on system power demand and provides an external Enable pin that reduces the current to just 2.3µA in shutdown mode.

Additional features include support for power sequencing and synchronisation to an external clock. Built-in safety and protection include soft-start, over-temperature protection, current limiting with pulse-by-pulse sensing, over-voltage protection, and adjustable under-voltage lockout (UVLO) according to the input voltage. There is also integrated compensation circuitry that simplifies design and saves bill-of-materials costs.

Three L7983 variants are available, comprising the L7983PU33R with 3.3V fixed output voltage, L7983PU50R with 5.0V fixed output voltage, and L7983PUR with adjustable output voltage. An associated evaluation board is available for each. The STEVAL-L7983V33 accelerates design with the L7983PU33R. The STEVAL-L7983V50 and STEVAL-L7983ADJ support the L7983PU50R and L7983PUR respectively.

The L7983 is in production now and available in a three by three millimetre DFN10 package, from $1.00 for orders of 1,000 units.