To bring some sort of order to a mobile world driving for completely tetherless operation with no wires – not even to a battery recharging station – device manufacturers and their suppliers in recent months have responded with three different standards for resonant or inductive – and hands off – recharging of battery-based systems.
To make it possible for mobile device manufacturers to build their systems without worrying about which “standard” is used – A4WP, PMA or WPC, Broadcom has just released its BCM59350, a multi-standard smartphone power management unit (PMU).
It does this by allowing automatic selection between specifications from all three leading standards organizations including the Alliance for Wireless Power (A4WP), Power Matters Alliance (PMA) and Wireless Power Consortium (WPC) for OEM flexibility.
A4WP uses resonant technology, called Rezence, that allows consumers to “drop and go,” placing multiple devices on a single charging surface without the trouble of accurate positioning or alignment. Rezence uses Bluetooth Smart technology as a communication channel between the smartphone and charging surface, taking advantage of the wide deployment of Bluetooth in mobile devices and wearables.
The Wireless Power Consortium's Qi specification makes use of a power transmission pad and a compatible receiver in a portable device. To use the system, the mobile device is placed on top of the power transmission pad, which charges it via resonant inductive coupling. The Power Matters Alliance (PMA) specification uses loosely coupled coils for easier charging .
Also different is the frequency range over which the inductive schemes do their work. WPC’s Qi inductive standard operates at 100 to 200 kHz, PMA’s resonant technology runs at 200 to 300 kHz and the A4WP’s Rezence technology usest 6.78 MHz, a spectrum reserved for industrial, medical, and scientific use.
To provide compatibility with all three standards, Broadcom’s SoC incorporates a frequency detector circuit that allows automatic selection among the differing specifications. According to Rahul Patel, Broadcom Vice President and General Manager, Wireless Connectivity Combos, the SoC can be added into the hardware of a handset or as an accessory in the form of a wireless charging sleeve, but it does not allow for resonant and inductive devices to charge on the same charging pad.
Broadcom has developed a resonance charging pad, but it is not multistandard compatible because resonance charging requires Bluetooth to communicate between receiver and transmitter, while inductive charging relies on load modulation.
Broadcom’s chip also incorporates a number of switches that allow Bluetooth to be used to gather charge and connect to the resonant charging pad.in an otherwise dead phone. When placed on a pad, beacon signals will detect the presence of Bluetooth and charge the chip enough to connect.
The chip is currently sampling and will be in mass production by the second quarter of this year.