High-Efficiency Mini Point of Load Converter ICs from Renesas

Recently, there have been two changes in power supplies market. The first is the requirement for reduced power consumption to achieve an energy-saving society, and the second is the increasing diversity in supply voltages required by increasingly highly functional semiconductor products such as microcontrollers and SoC devices.

To satisfy the first requirement, the new RAA20770X devices perform high-efficiency power conversion during normal load and - typically 90 percent of the time - also execute the frequent transitions to low-power mode quickly. As a result, they reduce overall system power consumption and help enable an energy-efficient society.

To satisfy the second requirement, although mounting area is spreading according to electric source increasing, the RAA20770X devices achieve a size reduction of about 75 percent compared to earlier Renesas products, featuring an ultra-miniature wafer-level chip size package that is essentially the same size as the chip itself. Furthermore, since no wired connections are required within the package, resistance in the wiring is reduced, which contributes to more efficient voltage conversion. The RAA20770X Series represents the first devices with this level of integration in this small a package size.

Key Features of the RAA20770X Series POL Converter ICs:

1) Contributing to system miniaturization with an area reduced by about 75 percent
In the RAA20770X products, Renesas adopted a wafer-level chip size package to achieve POL devices that can supply large amounts of current in a miniature form factor making it possible to reduce the IC's internal wiring resistance and package wiring resistance to an absolute minimum. For example, in the RAA207701GBM, which has a maximum rated current of 10 A, the package size is an extremely small 2.7 × 3.4 mm, which corresponds to a roughly 75 percent reduction in package size compared to earlier Renesas SiP POL products. Furthermore the thermal resistance from the package surface to the chip junction area is an extremely low 1℃/W, allowing a high thermal dissipation design when used with a heat sink and air flow.

2) Support for increased battery life
The next generation of notebook PCs will require functions similar to the information update and acquisition in standby mode (Connected Standby) provided by current tablet PCs and cell phones. It will be necessary to limit power consumption as much as possible in Connected Standby mode. To address this need, the RAA20770X Series devices adopt a constant on-time control method [Note 2], and in low power consumption modes where the load current is low, they achieve a low power consumption of about 0.5 µW. Another advantage of this constant on-time control method is that the POL converter's power consumption can be reduced by lowering the operating frequency, achieving the reduced power consumption of 1.6 mW when there is no load and 0.5 µW in standby mode. The constant on-time control method also provides the advantage of fast response. For example, even when rapid current increases occur when electronic equipment switches from an energy-saving mode to normal operation, the converter can respond instantly by increasing the operating frequency.

3) Ease of design for high-reliability power supply systems
The RAA20770X Series devices integrate the various protection functions, such as overcurrent, overvoltage, and thermal protection, required in POL converters - all on the same chip. As a result, these devices support safe and highly flexible high-reliability power supply system design with a minimal number of external components for easier design and reduced bill of materials. Furthermore, the output voltage and operating frequency can be modified to match the application they are used in, offering flexibility for operation in a wide range of applications.

4) Support for single-voltage power supply design
The new RAA207703GBM, RAA207704GBM, and RAA207705GBM devices include an integrated 5 V low dropout regulator circuit, which can provide the 5V required internally by the power supply controller, thus eliminating the need for an external power supply. This enables a system to operate from just a single-voltage using, for example, a 12 V power supply rail.

In addition to combining the power supply controller and driver controller IC, the RAA20770X Series devices integrate, on a single chip, two power MOSFETS that are optimal for POL converters that step down an input voltage of 5 V or 12 V to the 1 V or 3.3 V used by large-scale ICs such as ASICs. For example, the RAA207701GBM device features a maximum rated current of 10 A, and for a 12 V input and 3.3 V output, it can achieve high-efficiency power conversion from the low-current area to the high-current area - in particular, an 89 percent efficiency at 10 mA, a 95 percent efficiency at 4 A, and a 92 percent efficiency at 10 A. This power conversion efficiency, contributes to lower power overall in end-use products.

Samples of the RAA20770X Series POL Converter ICs will start in December 2012. Mass production of the RAA20770X devices is scheduled to begin in March 2013 and is expected to reach a scale of 500,000 units per month in July 2013.