Diodes Incorporated has introduced the AP3440, a pwm synchronous-buck dc-dc converter for low-voltage, high-density power systems. 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 synchronized with an external system clock applied to the same resistor input pin. A wide supply voltage range, 2.95V to 5.5V, makes the AP3440 well-suited for both 3.3V and 5V bus systems.
Packaged in the 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 as high as 94%. The AP3440 ensures excellent line and load regulation, with its current mode control providing fast transient response and cycle-by-cycle current limit.
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 is easily increased by programming the threshold using a resistor divider network on the enable pin.
To help minimize inrush currents and to support power-up sequencing, the AP3440 also integrates a soft-start function, programmed via an external capacitor. The inclusion of an open-drain 'Power Good' output signals that the device output is within 93% and 107% of its nominal voltage and helps to further reduce circuit footprint. The AP3440 buck converter is priced at $0.25USD each in 10k quantities.