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Power Electronics

Programmable Buck Converter Helps Reduce Solution Size

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 200 kHz to 2 MHz, 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, 2.95 V to 5.5 V, makes the AP3440 well suited for both 3.3 V and 5 V 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 4 A 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 2.6 V, 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.  Further information is available from

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