USB battery charging rev. 1.2: Important role of charger detectors: Page 6 of 8

November 06, 2014 //By Mohamed Ismail
USB battery charging rev. 1.2: Important role of charger detectors
Mohamed Ismail of Maxim Integrated considers the role of charger detectors in the USB battery charging specification rev. 1.2:

detector block diagram.

Over the last few years, smartphones took the world by storm. One of the major forces driving this sleek technology is form factor. As the list of features continues to increase while overall sizes are shrinking, careful planning and integrated solutions must be implemented to achieve the target shrinking specifications. Take, for example, a mobile phone that uses a single connector for charging; connecting to a PC; connecting to external accessories; or audio playback. To accomplish all of these tasks in a compact manner, system designers can opt to use a charger detection IC such as the MAX14656 (Figure 4).


Figure 4. A smartphone application using the MAX14656 charger detector.

This universal charger detection circuitry automatically distinguishes between different BC1.2-compliant ports and supports detection of most of the Apple proprietary chargers (e.g., 500mA, 1A, 2.1A). This device also has integrated DPDT switches, which allows the D+ and D- lines to be shared by a Hi-Speed USB transceiver, audio outputs, or even an internal UART. Using an I 2C interface, the embedded processor reads whether a charger has been attached and configures the internal switches for the appropriate mode. When you consider the built-in OVP on the VBUS pin, the ESD protection on the data lines, and the 1.65mm x 1.65mm footprint, this single charger detector adds considerable versatility in a single connector for space-constrained designs.
The Promise for Portable Electronic Devices

Charger detection technology is so versatile because the basic charger detector functions can be coupled with a variety of other features to provide highly integrated circuits for manufacturers of portable electronics. Other solutions combine charger detection with Li+ battery-charging control in a single package. Some combine charger detection with USB self-enumeration. Today’s newest charger detector chips autonomously monitor the battery charge cycle in accordance with BC1.2, instead of tasking the embedded processor with manually adjusting the total current drawn for the

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