Renesas Electronics Introduces Lithium-Ion Battery Charge Controller with Support for Rapid ChargingDecember 20, 2012 by Jeff Shepard
Renesas Electronics Corporation announced the development of the R2A20057BM lithium-ion (Li-ion) battery charge controller IC for mobile devices employing one cell Li-ion batteries, such as digital still cameras and smartphones. The R2A20057BM integrates a step-down DC-DC converter and supports 2 A charging in very small package in the world's smallest class.
As digital still cameras, smartphones and other mobile devices gain higher levels of functionality, their current usage increases, requiring bigger capacity of Li-ion batteries, and larger currents for charging these batteries. However, systems for large-current charging employ multiple power metal-oxide-semiconductor field-effect transistors (MOSFETs) and discrete passive components, and large-scale heat emission structure under large-current handling, while they need mounting area compactness especially for mobile devices.
To solve these problems, the new R2A20057BM substantially reduces the mounting area by integrating multiple power MOSFETs and charging circuits in a single chip, using a wafer-level package, a packaging technology that can also supply large amounts of current due to reduced package resistance. In addition, it incorporates a highly efficient on-chip step-down DC-DC converter to realize large-current charging while keeping heat generation to a minimum.
The use of a very finer high-voltage-tolerance wafer process and wafer-level package (WL-BGA, 25-pin, 0.4 mm pitch) allows Renesas to achieve a compact chip size in the world's smallest class of only 2.47 mm x 2.47 mm. In addition, the integrated 2 MHz high-frequency step-down DC-DC converter enables a use of compact multi-layer-chip inductors as the external devices. The 25 V on-chip, high-input voltage-tolerance enables a built-in overvoltage protection circuit and eliminates an external overvoltage protection circuit, contributing to a substantial reduction in the mounting area.
The new R2A20057BM automatically identifies six USB port types, including the three types stipulated in the USB Battery Charging Specification, Revision 1.2, and sets the input current limit value automatically.
The new R2A20057BM can implement charging operation as a standalone product, or can optionally be controlled through command input via Inter-Integrated Circuit (I2C). The I2C control commands support a wide range of requirements, covering charge start/stop control as well as the ability to change parameter values such as charge control voltage, charging current, and input current limit value.
The new R2A20057BM can control the power supply path to the system while the battery is charging using a built-in load current distribution function that prioritizes supply of power to the system and adjusts the charging current when the input current is limited, e.g., when power is being drawn via a USB interface. This eliminates the need to add large external components such as discrete switches when building a charging system.
The built-in protection functions ensure safe charging by providing input/output overvoltage protection, thermal protection, charge timer protection, and thermistor-based battery temperature monitoring. The high-precision charge control voltage of 4.20 V/4.35 V ±0.5 percent enables safe charging of Li-ion batteries at the specified voltage. Samples of the R2A20057BM battery charge controller IC are available now, priced at US$4.0 per unit. Mass production of the R2A20057BM devices is scheduled to begin in January 2013 and is expected to reach a scale of 500,000 units per month in August 2013.