Date: 23/12/2008

Buck converter using valley current-Mode control

Allegro launched a buck converter, A4403 that 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 and low output voltages. This converter is a flexible and cost-effective solution for office automation, industrial and consumer applications.

The switching frequency is maintained constant, as the input voltage modulates the on-time. This feed-forward control ensures good 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.

Some of the other features are listed below:

1. High input voltages (9 V - 46 V)
2. Low output voltages (0.8 V - 15 V)
3. High switching frequencies of up to 2 MHz
4. Minimal external components are required
5. Optimal drive circuits are utilized to minimize switching losses
6. Internal housekeeping and bootstrap supplies are provided
7. Internal diagnostics provide protection against overcurrent, input under-voltages, and overtemperature conditions
8. A top-off charge pump is also provided to ensure correct operation at light loads

Packaging: 16-contact, QFN (suffix EU),
Size: 4 mm x 4 mm x 0.75 mm

Further information about Allegro can be found at www.allegromicro.com