In a synchronous-rectification circuit converting a 12V DC input to a 1.1V DC output at 600 kHz switching frequencies, it achieves an efficiency rating of 91.6 per cent. Output current doubled from earlier dual-type power MOSFETs from Renesas Technology.
The higher power supply efficiency of RJK0383DPA has two important benefits. It uses a small WPAK3 package that reduces the chip mounting area to about half that of a dual-package power MOSFET configuration, offering the same level of power supply efficiency. It also allows the device to deliver more output current. Smaller synchronous-rectification DC/DC converters are thus enabled, facilitating the higher mounting densities eagerly sought in mobile devices and other products in which small size adds convenience.
“A two-package configuration made it possible to raise the power-supply efficiency of synchronous-rectification DC/DC converters so the output current could be increased without adding more power MOSFETs,” said Tetsuo Sato, director, solutions business unit, Renesas Technology America. “On the other hand, dual-type products that integrate two power MOSFETs in a single package have the advantage of having a smaller mounting area. However, the power-supply efficiency of these dual-type products was not as good as that of two-package configurations, so their maximum output current was lower. The market clearly desired a dual-type power MOSFET product with improved power supply efficiency and more output current to meet the space limitations of mobile devices. The new RJK0383DPA device directly addresses this need.”
The high-side power MOSFET in RJK0383DPA has a drain-gate load (Qgd) of only 1.5nC (at VDD=10V) for a fast switching speed and correspondingly high efficiency. The device’s low-side power MOSFET has a low on-resistance (RDS (on)) of 3.7mW (typical, at 4.5V) that reduces power loss.
Additionally, the device integrates a Schottky barrier diode (SBD) that is connected via low-inductance wiring to the low-side power MOSFET. This design speeds up the switching of current flow to the SBD during the DC/DC converter’s dead time, for less power loss. It also suppresses voltage spikes during switching, thereby reducing noise.
The advanced semiconductor manufacturing process that Renesas uses to fabricate RJK0383DPA achieves lower loss and higher efficiency than the previous ninth-generation process. On-resistance is about 30 per cent lower, while the opposing characteristics of gate charge capacitance (Qg) and drain-gate load (Qgd) are approximately 27 per cent and 30 per cent lower, respectively.
With a price tag of $0.89, the new RJK0383DPA device would be available in Q4 2008. |
