Allegro Microsystems Announces New Valley Current Mode Control Buck Converter
Allegro MicroSystems, Inc. has added a new 3A 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 suitable for applications that require high switching frequencies combined with high input voltages (9 – 46V) and low output voltages (0.8 – 15V). The A4403 buck converter is suitable for office automation, industrial and consumer applications.
The company claims that 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 is said to ensure 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 � 4 x 0.75mm QFN (suffix EU), with exposed pad for enhanced thermal dissipation. It is lead (Pb) free, with 100% matte tin leadframe plating. The A4403 is priced at $0.76 in quantities of 1,000.
