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Allegro MicroSystems, Inc. Announces New Valley Current-Mode
Control Buck Converter
Flexible Solution for a Wide Range of Applications 
Worcester, MA – January 13, 2009 — Allegro® adds a new 3 A buck converter to their existing family of general-purpose buck regulators. This new device uses valley current-mode control. This control scheme allows very low switch on times to be achieved, making it ideal for applications that require high switching frequencies combined with high input voltages (9 V - 46 V) and low output voltages (0.8 V - 15 V). Allegro’s A4403 buck converter is a flexible and cost-effective solution for office automation, industrial and consumer applications.
System cost is reduced through high switching frequencies of up to 2 MHz, allowing smaller and lower value inductors and capacitors. In addition, minimal external components are required through high levels of integration. Optimal drive circuits are utilized to minimize switching losses. The switching frequency is maintained constant, as the input voltage modulates the on-time. This feed-forward control ensures excellent line correction. An external resistor pulled up to the input supply programs the on-time.
When power is initially applied and the device is enabled, a user-configurable soft-start function occurs to minimize inrush current and to prevent output overshoot. Internal housekeeping and bootstrap supplies are provided which only require the addition of one small ceramic capacitor. A top-off charge pump is also provided to ensure correct operation at light loads. Internal diagnostics provide comprehensive protection against overcurrents, input under-voltages, and over-temperature conditions.
Allegro’s A4403 is supplied in a 16-contact, 4 mm × 4 mm, 0.75 mm QFN (suffix EU), with exposed pad for enhanced thermal dissipation. It is lead (Pb) free, with 100% matte tin leadframe plating.
About Allegro
Allegro MicroSystems, Inc. is a leader in developing, manufacturing and marketing high-performance power and Hall-effect sensor integrated circuits. Allegro's innovative solutions serve high-growth applications within the automotive, communications, computer/office automation, consumer and industrial markets. Allegro is headquartered in Worcester, Massachusetts (USA) with design and applications centers located in North and South America, Asia, and Europe. Further information about Allegro can be found at www.allegromicro.com.
Editorial Contact:
Stephanie Fennelly
Director - Marketing Communications
Tel: (508) 854-5363
sfennelly@allegromicro.com