Diodes Incorporated — AP62500 and AP62800 DC-DC Converters

The latest synchronous buck converters from Diodes Incorporated give engineers the flexibility to develop point-of-load (PoL) power supplies that are optimized for either efficiency or size. The AP62500 and AP62800 feature selectable switching frequencies, and a choice of three operating modes that increase efficiency, reduce ripple or eliminate audible noise.

The new dc-dc converters from Diodes require a small number of external components, enabling design engineers to realize compact power-system implementations.

The AP62500 has a continuous output-current rating of 5 A, while the AP62800’s rating is 8 A. Both buck converters operate from a wide input-voltage range: 4.5 V to 18 V for the AP62500, and 4.5 V to 17 V for the AP62800. The devices’ output voltage can be adjusted down to 0.6 V. This makes the converters ideal for point-of-load power supplies in high-volume consumer products that operate from a 5 V or 12 V distributed power bus. They also provide an efficient solution for FPGA, DSP, and ASIC power supplies.

The selectable switching-frequency options are 400 kHz, 800 kHz, and 1.2 MHz. At a lower frequency, the design achieves higher conversion efficiency, and at a higher frequency the size of the power supply’s magnetic components can be reduced.

There are three selectable operating modes:

• Pulse frequency modulation (PFM) for high light-load efficiency
• Pulse width modulation for low output-voltage ripple
• Ultrasonic, to operate outside the audible frequency range and maintain the switching frequency at higher than 20 kHz

The design of these buck converters minimizes EMI problems. A proprietary gate-driver design mitigates switching-node ringing without having to extend MOSFET turn-on/turn-off times, which would otherwise limit the device’s ability to switch at high frequency. Constant-on-time control results in fast transient response and low output-voltage ripple, as well as providing for better loop stabilization.