Authentication, over-voltage protection, and compact form factor are key challenges in implementing power delivery feature in the next-generation USB designs.

The USB Type-C™ standard is quickly gaining traction and one of its key highlights is the mechanism that delivers up to 100 watts of power over the USB interface. The adoption of the USB power delivery (USB-PD) feature is now a key mobile trend in AC adapters, notebooks, tablets, smartphones, etc.

So far, the mobile industry has relied on proprietary fast-charging techniques that employ USB Micro-B connectors. But recent incidents with Li-ion batteries have underlined the need for a safe power delivery ecosystem and USB-PD circuitry promises just that.

The USB-PD mechanism facilitates higher power demands and faster charging for compatible devices compared to previous USB charging technologies. And it uses a dedicated configuration channel (CC) line that functions independently of conventional USB data transmission.

Here are three major issues that developers face while creating rapid-charging applications in mobile devices.

 

1. Authentication

In USB-PD protocol, the connected devices negotiate power requirements and enter into an agreement to determine the optimum voltage and current levels. It's a critical requirement that enables USB product manufacturers to examine the genuine origin of devices like cables and chargers before starting the high-power charging.

Authentication ensures the identity of the device, making it easier to tell if it's a genuine or counterfeit device. Take, for instance, the R9J02G012 USB controller chip from Renesas. It allows USB ports to electronically verify and trust the authenticity based on the certificates and public key infrastructure (PKI) implemented in the USB Type-C Authentication specification.

Renesas claims that, in its new USB port controller chip, it has incorporated highly tamper-resistant technology that the Japanese chipmaker has been using to secure its MCUs against cyber attacks.

 

The R9J02G012 controller chip integrates USB PD 3.0 and USB Type-C Authentication functions in a single package. Image courtesy of Renesas.

 

2. Form Factor

Size is another vital consideration in USB-PD designs. That Renesas' USB port controller, for example, is a single package that supports both USB PD 3.0 and USB Type-C Authentication standards.

These two functions have so far been implemented with two separate chips. A single-package solution reduces the mounting area in cables and electronic devices. According to Renesas, the board mounting area for the new R9J02G012 USB controller is 50 percent less than the area used by the company's existing R9A02G011 chip. Currently, the 40-pin QFN  package is 6 mm x 6 mm and the 42-ball BGA is 3.6 mm x 3.1 mm.

This is comparable to competing chips, such as the TPS65982 controller chip from Texas Instruments which also measures 6 mm x 6 mm. 

 

3. Internal Protection

The USB-PD hardware demands complex interface electronics to efficiently negotiate power delivery with connected devices. For example, the power delivery range—from 5V/0.5A to 20V/5.0A—mandates the built-in protection against the risks posed by over-voltage.

 

ST's USB controller chip allows cables to be disconnected safely using a discharge circuitry for the VBUS and VCONN power lines. Image courtesy of STMicrolectronics.

 

STMicro's new USB Type-C port controller claims to provide internal protection without adding an external voltage regulator, thus saving component count and board real-estate in USB designs. The STUSB4710 controller chip can handle the entire connection setup without external CPU involvement and supports up to five power delivery profiles (PDOs).

 

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