STMicroelectronics Adds Hybrid Control to USB-C PD Sink

USB-C powered equipment increasingly requires support for both standard charging and advanced USB Power Delivery (PD) functions such as role swapping and Alternate Modes. Within this context, STMicroelectronics has introduced a patented hybrid control mode in its STUSB4531 USB PD sink controller to simplify implementation of these features while retaining software-free operation for basic power negotiation.

Hardware PD stack with software-free baseline operation
The STUSB4531 integrates a certified, hardwired USB PD protocol stack combined with ST-proprietary AUTORUN algorithms. This architecture enables automatic negotiation, supervision, and management of power contracts without requiring a host microcontroller to run the full PD stack.

The updated AUTORUN algorithms allow devices to negotiate optimal power profiles with USB-C AC adapters, including Adjustable Voltage Supply (AVS) and high-power charging in dead-battery mode. These capabilities are relevant in battery-powered and VBUS-powered products such as portable audio devices, wearables, set-top boxes, Wi-Fi access points, healthcare electronics, and lighting systems, where minimizing firmware complexity can reduce development time and validation effort.

Hybrid mode opens access to advanced USB PD features
The new hybrid mode allows an external application processor to interface with selected layers of the internal PD stack. Instead of implementing the full protocol in firmware, designers can access higher-level PD functions while the controller continues to manage low-level timing and signaling.

This approach supports features such as battery status messaging, data-role swapping, Alternate Modes, and vendor-defined messages (VDM). These capabilities are often required in products that combine charging with data or video, including hard disk drives, point-of-sale terminals, printers, drones, portable industrial devices, VR headsets, infotainment systems, portable displays, and gaming consoles. Alternate Modes enable interfaces such as DisplayPort or Thunderbolt over USB-C, while VDM is used for accessory and medical device extensions.

Compliance with USB-C and regulatory frameworks
The STUSB4531 is certified to USB-C^® 2.4 and USB PD 3.2 specifications and complies with IEC 62680, supporting alignment with European regulatory requirements linked to common charging standards. These certifications are important for manufacturers targeting markets where USB-C charging interoperability is mandated as part of broader power management and product standardization efforts.

Development tools and integration support
To support implementation, STMicroelectronics provides an ecosystem that includes the EVAL-SCS007V1 evaluation board and the certified minimal reference design EVAL-SCS006V1. Configuration and testing tools include the STSW-STUSB020 graphical user interface and the STSW-STUSB021 NVM flasher. An open-source software library, STSW-STUSB022, is planned to extend integration options for developers working within embedded firmware environments.

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