Our last four sessions have taken us through an overview of USB PD technology and related Renesas solutions. This time, we look at the actual steps a developer would follow when designing a USB PD product.
USB PD Standards Mark a Mega Change in Power Supply Implementation
In our previous sessions we’ve seen how USB PD standards significantly change power supply conditions for both computers and peripherals. Interconnection becomes quite straightforward when all devices are compliant: an AC adapter and hub can provide power to the computer, the monitor, the hard drive, and other peripherals, with USB Type-C™ cables connecting all devices.
Prior to the advent of USB PD, two cables would be required for each device (with the exception of those that can run on bus power): a USB cable to transfer data, and a power cable. From now on, much excess wiring can be eliminated because a single USB Type CTM cable can transfer both data and powers.
Renesas is ready with a variety of solutions to facilitate the development of PD-compliant devices. These solutions support full implementation of the safety policies covered by the standards, and can greatly simplify the work required to design compliant products.
Let’s look how development proceeds when these solutions are used.
First Plan the Product, and Then Select the Solution
When planning a product, first decide on its power role. A PD-compliant product which port is for supplying power over VBUS (Source: such as an AC adapter, DC/DC module, etc.), or which port is consuming power from VBUS (Sink), or which port is capable of operating as either a Source or a Sink (DRP: such as hub or power bank). Next, decide on the voltage and current values to be supported (if Source) or to be requested (if Sync), and also decide whether to support C-AUTH or not.
If the product will be related with charging, also consider whether to implement a Programmable Power Supply (PPS), allowing for high performance and fine control of voltage and current changes. A PPS can cut wasted energy, lessen the need for heat-tolerant design, and reduce charging times—all attractive features for potential purchasers.
Once you have decided on the general feature of your product, it’s time to focus on the detail design. You are now ready to turn to the “Renesas USB Power Delivery Family” of solutions. First select one of the family’s USB PD controllers (PDCs); and, if the product will operate as a Source, select the Renesas or Intersil power IC that best meets your requirements.
When using Renesas solutions to develop a PD-compliant product, you will need to write the firmware that defines the desired functionality into the PDC, and you will then need to build an actual product board. Here we will briefly show how you can use a Renesas evaluation board, design kit, and firmware creation tools to carry out these tasks. Note that the term RDK (Reference Design Kit) refers collectively to the evaluation board and design kit.
When using an RDK, the development steps are as follows.
- Procure the RDK from a distributor.
- Use the firmware creation tools to customize the parameters, and use the evaluation board to check that the firmware is operating as expected.
- Develop a real board that incorporates the USB PD circuitry with reference to the design kit.
- Write your custom firmware into the USB-PD IC on the board, and evaluate the board’s operation.
Now let’s take a closer look at each step.
Step 1: Procure an RDK
RDKs of Renesas USB Power Delivery Family can be obtained through the relevant distributor. Note that the evaluation board in RDK cannot currently be purchased, but is provided on loan. The RDK also includes an instruction manual, circuit diagrams, bill of materials, wiring pattern drawings and layouts data.
RDKs provides a general-purpose USB converter (for developing sink-side products), a DC/DC module (for source-side products), a PD hub (for DRP products), and other developments are progressing also. Evaluation boards come in two varieties—one with authentication capability included, and one without—so that you can choose the one that best meets the needs of the product. RDKs for source-side products include an RAA230161 or an Intersil-made power IC.
Step 2: Customize the Firmware
The firmware determines the operation of the evaluation board's PDC. Core PDC operations has been completed, and the developer can customize as necessary to meet specific product needs by selectable options such as preset, using the PDC Image Generator tool. When using this tool, you first create a project and then select the desired type of PDC functionality (see Fig. 1.). You are then presented with an easy-to-use GUI that lets you customize the pin assignments (Fig. 2.), the Power-Rule parameters, and other operational features.
In this example, Pin 3 is being assigned as the temperature alarm output. Before you can define a PDC function, you must assign the function to a pin.
Once you have set the functions for your product, the PDC Image Generator will generate a flash memory image that you can proceed to write into the PDC. There are several ways to write to the PDC, as shown in Figure 3.
Once the image has been written into the PDC, it is time to run the evaluation board to see that the logic works as expected.
Step 3: Develop a Real Board
Now it's time to develop an actual board. Use the design kit's circuit diagrams, bill of materials, wiring pattern drawings and a layout data as a reference when adding the desired USB PD functions for the product being developed. This completes the hardware development.
Step 4: Confirm that the Real Board Operates as Expected
Now write the firmware developed in Step 2 into the PDC on the real board developed in Step 3. Use the same writing procedure that you used at Step 2 to write into the evaluation board. After completing the write, confirm that the board operates as expected. If so, you’re done.
Time Reduction with RDKs
RDKs have been effectively used in the development of many products. If you already have experience in the use of Renesas USB PD solutions, you can skip the steps with the evaluation board and go directly to develop the circuit and patterns with reference to the design kit.
Renesas has already confirmed that these circuit and pattern drawings operate correctly. As a result, the design kit can save you considerable development time by eliminating the need for poring over IC documentation while working out your drawings and patterns. Please keep in mind that not just Renesas semiconductors but Renesas solutions offer comprehensive technologies and information that can be used effectively when developing products.
In these five sessions we have looked at the USB PD standards and related Renesas solutions. As we have seen, USB PD standards make it possible to use one USB Type-C™ cable for both data and power, allowing for much less clutter and eliminating the need for a separate AC adapter for each product. Benefits accrue not just to users, but to the environment as well.
Going forward, we expect an acceleration in the use of USB PD for various charging applications. We encourage developers to consider the use of Renesas solutions for short term product development.
- 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