Programmable buck converter reduces footprint

With its switching frequency programmable over the range 200kHz to 2MHz, the device enables a reduction in the size of external inductors and capacitors and simplification of power supply design. The buck converter's operating frequency is set using a timing resistor and is also easily synchronised with an external system clock applied to the same resistor input pin. A wide supply voltage range, 2.95 to 5.5V, makes the AP3440 well suited to both 3.3 and 5V bus systems. Packaged in a thermally enhanced V-QFN3030-16 package and integrating a pair of very low on-resistance N-channel power MOSFETs, the converter is capable of driving a 4A load at an efficiency level up to 94%. The buck converter's built-in protection features include over-current and over-voltage protection, thermal shutdown, and a programmable under-voltage lockout (UVLO) function. The UVLO level is internally set at 2.6V, but can be increased by programming the threshold using a resistor divider network on the enable pin. To help minimise inrush currents and to support power-up sequencing, the AP3440 also integrates a soft-start function, programmed via an external capacitor.