Battery interface update trends towards ‘smart’
Released in June, the MIPI BIF v1.1 is a single-wire hardware and software interface for connecting a power management chip in a phone to a smart or low-cost rechargeable battery. This facilitates communication of battery characteristics for ensuring safe and efficient charging control under all operating conditions.
Among the release's most notable features is a fuel gauge function to monitor the conditions characterising battery health. At the same time, companies can develop their own battery charging parameters to ensure safe operation and maximise battery life.
"The battery is a critical component in a mobile device and its deployment in a product has direct impact on the consumer experience and the mobile device ecosystem," said Joel Huloux, chairman of the board of MIPI Alliance. "MIPI BIF v1.1 will give companies a set of functions they can use to develop innovative, service-differentiating battery functions while improving battery safety-all via this single interface solution."
BIF system diagram. Source: MIPI Alliance
The smart battery interface supports multiple Slave devices within the battery packs or mobile device Host. It defines the digital communication interface physical layer electrical requirements and characteristics, protocol and basic data architecture information for a mobile device Host and the Slaves in the battery pack with sufficient detail to allow development of the interface.
Alternatively, BIF itself specifies measurement range and accuracy for low-cost battery packs where the only source of information is a pull-down resistor. The specific measured resistor value assignment for capacity and chemistry, among others, is left to the mobile device manufacturers.
BIF includes Hardware Abstraction Layer (HAL) specification, which defines a software interface to simplify the adoption of BIF on common host platforms. MIPI claims that BIF is the only mobile-to-battery communication interface specification in the industry, offering manufacturers a uniform solution to replace proprietary interfaces.
The specification will indeed work to the manufacturers' advantage since higher power densities and advanced battery features involve chemistries that require new battery control and management, said Wolfgang Furtner, vice chair of the MIPI Alliance Battery Working Group.
"Manufacturers need a smart battery interface to take advantage of these capabilities and with MIPI BIF v1.1, they now have the opportunity to enable these features and extend the benefits of smart batteries to more products."
MIPI BIF is already supported by multiple mobile chipset manufacturers and battery IC manufacturers and has been successfully adopted for use in smart phones that are commercially available on the market for consumers. Companies that are using the specification include Infineon, Microsoft, Mitsumi, Sharp, STMicroelectronics, and UNH-IOL.
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