ROHM's wireless power receiver IC to serve smartphones and other portable devices



Qi Standard Expansion and Development Roadmap

ROHM has recently announced the development of a wireless power receiver IC designed to charge smartphones and other portable devices. The BD57011GWL is compliant with WPC’s (Wireless Power Consortium) latest Qi Low Power Ver1.1 standard for wireless power transmission and features low heat generation in a monolithic design, reducing temperature rise by up to 75% during wireless charging. This provides the ideal balance between mounting area and heat generation. In addition, the industry’s first misalignment detection function detects incorrect positioning of the target device on the charging pad, which can lead to decreased charging efficiency.

Wireless power transmission technology eliminates the need for a power cord for charging portable devices, is expected to improve the waterproof and dustproof properties of device connectors, and supports a variety of terminals with a single wireless charger. However, a major challenge with 5W-class wireless power transmission for smartphones and other portable equipment is the relatively large amount of heat generated during charging.

Key Features
-Low heat generation in a monolithic (single-chip) design
Cutting-edge BiC-DMOS processes are utilized for the lowest MOSFET ON resistance possible. This, along with an optimized monolithic design, provide an ideal balance of small mounting area with low heat generation, reducing temperature rise during wireless power charging by approximately 75% compared with conventional solutions.
-The industry’s first misalignment detection function improves charging efficiency
During charging, incorrectly positioning the target device on the charging pad may cause a significant drop in charging efficiency. To prevent this, ROHM has included a misalignment detection function that triggers an alarm, allowing the user to reposition the device to achieve maximum charging efficiency.

WPC Qi Low Power Ver1.1 Standard
The latest international wireless power transmission standard, Qi Low Power Ver1.1, was established by WPC in April of 2012. The difference between this latest standard and Low Power Ver1.0, established in 2010, is that Ver1.1 includes the requirement for a built-in FOD (Foreign Object Detection) function to improve safety. ROHM has joined as a full member of WPC, which is comprised of a maximum of 25 companies, and plays an active role as a consultant as well as in the development of the increasingly popular Qi wireless power transmission standard.

FOD (Foreign Object Detection) provides a greater level of safety
FOD is required in the latest Qi standard in order to prevent chassis deformation and/or burns due to excessive heat generation of a foreign metallic object when placed between the transmitter and receiver, dramatically improving safety.
FOD involves complex calibration of the receiver and transmitter, achieved in this case by combining ROHM’s renowned analog technology together with ROHM Group LAPIS Semiconductor’s industry-proven digital expertise.
Furthermore, since the power loss is calculated at the receiving end, the different loss error for each receiver can be fine-tuned via external resistor, ensuring flexible, high-precision FOD operation.

Qi Standard Expansion and Development Roadmap
The Qi standard is expanding the compatible power range to meet the growing needs of the wireless power transmission market. In response to this, ROHM is currently developing power receiver control ICs and products designed specifically for the medium power (5W+) sector, using a variety of core technologies required for wireless power transmission cultivated by ROHM Group companies.