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Data servers are on duty 24/7, allowing us to communicate whenever we want, but also ensuring that all our electronic-based daily lives run smoothly and safely - and that's not all we could think of. A failure in the server supply can cause expensive losses and, in the worst case, lead to critical situations - just think of emergency calls, health services or air traffic control. For this reason, server stations are always equipped with a battery back-up, operating on either 24 V or 48 V DC.

The battery management and charging circuit is controlled by low-voltage electronics at 5V or even 3.3V, the typical supply voltage for microcontrollers. These supply voltages must be generated from the higher battery levels. As the circuits operate in stand-alone mode without human intervention, there is no need to use isolated switching topologies. A simple step-down or buck converter can do the job with high efficiency and the required reliability. It consists of a MOSFET and a so-called buck diode, usually a Schottky. These are chosen for their low forward voltage drop and low switching losses.

As a rule of thumb, the safety margin between the DC voltage and the allowable Schottky reverse voltage should be between three and six times the DC level. Only then can reliable operation be guaranteed, ensuring that potential voltage spikes remain well below the maximum ratings of the Schottky diode. The SK220SMA by Diotec Semiconductor is a high voltage Schottky diode offering an admissible reverse voltage of 200 V and forward current of nominal 2 A. It comes in the small yet powerful DO-214AC/SMA case outline measuring just 5 by 2.7 mm. Forward voltage drop is less than 950 mV at 2 A, and reverse leakage below 50 µA at 200 V, all at 25°C. This makes the parts ideally suited as buck diodes used in battery back-up systems of data servers.