USB PD standards mark an important advance in the safety and convenience of USB charging. Manufacturers wishing to independently implement these new features, however, must first read the standards carefully and then undertake the extra work required to build these new capabilities into their designs. However, manufacturers do not need to go this alone. Renenas stands ready with solutions that greatly simplify the work required to build USB PD–compliant products.
Two Key Devices, from Renesas
USB Power Delivery Revision 3.0 (below, “USB PD”) allows for delivery of power up to 100W through a single cable. The specification makes it possible to power multiple devices simultaneously, eliminating the need for a dedicated AC adapter for each device. It also provides two other important functionalities: FAST ROLE SWAP (FRS) allows devices to switch roles as power providers and power consumers; and PROGRAMMABLE POWER SUPPLY (PPS) makes possible for rapid charging without unnecessary heat. USB Type-CTM Authentication capability (below, “C- AUTH”) is another significant recent addition. Below, we look at USB PD features, and explain the new capabilities.
The R9J02G012 Controller IC, with Full C-AUTH Support
Released in May 2017, this is our latest USB PD controller IC. It complies with both PD 2.0 and PD 3.0. In addition to supporting basic PD operations, it also supports new features such as fast role swap (FRS) capability.
The R9J02G012 communicates, via the USB Type-CTM cable’s CC pin, with its counterpart USB PD controller on the connected device. The two devices go through numerous steps, determining which side will act as source or as sink, and then setting the power level (voltage and current) that the source will supply, based on the USB PD Power Rules. The controller IC must then continue to monitor for overvoltage, overcurrent, and over-heating. In the event that it detects any of these conditions, it must then take appropriate actions—as set forth in the standards—to limit any damage. The most distinctive feature of this controller IC is its ability to provide stand-alone support for C-AUTH, operating both as initiator and responder. Earlier models, such as the R9A02G011, had to be paired with an external secure MCU to implement this capability. Because this newer IC internalizes the MCU functionality, it delivers the same performance while cutting the board size to less than half.
Because of its small size, this controller IC is also ideal for building directly into USB PD-compliant cables. It provides the eMarker functionality required by these cables, making it easy to implement systems that use C-AUTH not just on devices but also on cables. In addition, this IC will conform to changes in product specifications by rewriting the data of internal flash memory.
The RAA230161, Small-Footprint Power IC
This DC-DC converter IC, with built-in power control MOSFET, can generate each of the four voltages required by the USB PD standards—5V, 9V, 15V, and 20V—and can output up to 60W (at 3A). Power efficiency is 95%, and it is possible to build products with reduced heat generation. Where previously it would have been necessary to use four separate DC-DC converter ICs to support the four required voltages, this new IC supports all of these on a single chip, cutting the space usage in half.
The RAA230161 built-in circuitry includes overvoltage, overcurrent, and over-heating detection, short-circuit protection, and a watchdog timer (WDT). If the IC detects a sudden drop in output voltage, it will interpret this as a short and will promptly cut the power, thereby preventing a current surge that might overheat elements. The WDT triggers periodic monitoring, to confirm that the system continues to operate normally. In the event of a problem, it will generate a reset signal. When used in synergy with the R9J02G012 described above, the RAA230161 can be extremely effective in reducing board size and speeding up the development process. Of course, the RAA230161 can also be used very effectively with the earlier USB PD controllers, such as the R9A02G011. (See Fig. 2.)
Power ICs, Support for Charge Management and PPS Implementations
Renesas Intersil power management ICs are suitable for USB PD–based battery charging.
For example, buck-boost charger ICs are DC-DC converters offering both step-up and step-down capability, with support for a wide range of output voltages, and with the ability to regulate the charging of lithium batteries having anywhere from 1 to 4 cells.
The buck-boost charger is ideal when using a USB PD source to charge a lithium ion battery. In addition to monitoring for irregularities in the input voltage from the power adapter, it also monitors the cell voltages, and it includes built-in protection against overcurrent and over-heating.
The bidirectional buck-boost voltage regulator (BB VR) IC supports both step-up and step-down delivery of up to 20V, making it suitable for use in Programmable Power Supplies (PPS). A PPS, as explained in a previous session, allows for fine control of both voltage and current, and can regulate these as necessary to meet demand. A PPS implementation can generate the precise voltage required by the sink, curtailing any conversion loss or overheating at sink device.
The BB VR also supports fast role swap (FRS), and can quickly adjust operation to accommodate role swaps. Assume, for example, that a PC with a built-in BB VR is running on power from a USB PD power supply, where the PC is acting as the sink and is converting to the required voltages internally. Now suppose that the power source stops working, causing the PC to suddenly change its role from sink to source, as it begins to supply power to the outside. In this case, it becomes necessary to convert the outgoing voltage to the USB PD requirement. Because the BB VR is bidirectional, it can regulate the voltages for both sinking and sourcing, allowing full support for the role switching scenario described here.
Of course, the BB VR also includes built-in monitoring and protection: it monitors not only for overvoltage, over-current, and over-heating, but also for under-voltage; and it takes appropriate measures in the event that any of these irregularities are detected.
As you can see, Renesas offers a variety of ICs to support USB PD implementations. In the next and last session of this series, we will look at how these ICs can be used to support the development of source and sink devices.
- USB Power Delivery (1) Enhanced Convenience in USB Charging
- USB Power Delivery (2) The Technology - Convenience and Safety
- USB Power Delivery (3) USB PD Safety Implementation USB Type-C™ Authentication (C-AUTH) of Legitimate Devices
- USB Power Delivery (4) Renesas Solutions for USB PD
- USB Power Delivery (5) Faster Development with Renesas Solutions