Renesas MCU controls 1.5A USB charging

Renesas has announced microcontrollers capable of controlling 1.5A USB high-speed charging, claiming them to be industry’s first compliant 16bit MCUs.

Since the inception of USB, USB host ports have been capable of delivering 500mA from their 5V rail without the voltage collapsing – something that has been exploited to charge portable items like phones.

With the advent of the high-speed charging version of the USB specification (USB BC1.2), this current capability has been increased to 1.5A, and signalling has been specified to tell the charged item if 0.5 or 1.5A is available.

Called RL78/G1C, the microcontrollers enable USB BC 1.2 compliant high-speed charging and power supply control at the same time as USB data communications.

Capable of being used in the item to be charged, or the charging source, the firm has demonstrated prototypes of a portable charger whose internal battery is both charged and provides charge under the control of a RL78/G1C.


What is not included on the chip is any form of 1.5A regulator.

A Renesas reference designs proposes the firm’s R2A20056BM or 20057BM buck converter for when the MCU is controlling the charging of its associated battery, and a generic Li-ion to 5V boost converter when the MCU is managing the creation of 1.5A charging power.
Control over these external chips is through an included I2C interface.

By supporting the digital side of USB hosting, the chips are suitable for use in products that support plug-in USB memory, keyboards and mice, said the firm. “The group of MCUs is optimal for applications including industrial equipment such as data loggers, consumer equipment such as smartphone accessories, portable healthcare devices, USB chargers and AV accessories.

The first series within the RL78/G1C Group of microcontrollers will have 32 to 48pin packages down to 5x5mm, up to 32kbyte flash, up to 5.5kbyte RAM, and a 1% accurate clock oscillator.

Based on the firm’s RL78 core (31Dmips @ 24MHz), the microcontrollers achieve 71µA/MHz in full operation as well as 0.23µA RAM-retained sleep.

Samples are available now with mass production scheduled to begin in March 2013.

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