Posted to News on 15th Jan 2009, 10:32
Buck regulator IC achieves high (2MHz) switching frequencies
Allegro MicroSystems Europe's new A4403 is a 3A buck regulator IC that uses a valley current-mode control scheme to offer very low switch-on times, making it suitable for applications that require high switching frequencies combined with high input voltages and low output voltages.
A high step-down ratio, made possible by an 'on' time of less than 50ns, permits a wide output voltage range from 0.8-15V at 3A from an input supply voltage range from 9-46V. Standby current is less than 100uA.
This device's capability for high switching frequencies of up to 2MHz leads to the use of smaller and lower-value ancillary components such as inductors and capacitors, while the high level of integration means that a minimal number of external components are needed. As a result, the A4403 provides a compact, flexible and cost-effective option for industrial, office automation and consumer applications.
Optimal drive circuits are utilised to minimise switching losses, and 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.
User-configurable soft-start
When power is initially applied and the device is enabled, a user-configurable soft-start function is implemented to minimise 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 undervoltages, and overtemperature conditions. The device is rated for an operating temperature range from -40degC to +105degC.
Allegro MicroSystems' A4403 is supplied in a 16-contact, 4 x 4 x 0.75mm QFN package (suffix EU) with exposed pad for enhanced thermal dissipation. It is lead (Pb)-free, with 100 per cent matt tin lead-frame plating.
