Power Tips: How to program PMBus Devices

This blog provides a tutorial on programming TI digital parts using TI in-house tools.

TPS40422 and TPS40425 are two popular digital PMBus controllers which are used in many Point-of-Load (PoL) applications ranging from 10A to 100A. Both digital controllers are designed to start up without PMBus; however, they need to be programmed to fully utilize the benefits such as telemetry, sequencing and margining features.

TI Fusion digital power designer has a Graphical User Interface (GUI) which helps configure the parameters, monitor the telemetry in real-time and show all the register status. The tool offers online and offline versions. The offline version helps the user configure the devices without the need to connect to the live devices. The online version detects the live devices through a TI USB-to GPIO adaptor [link] and communicates with them in real-time.

TI Fusion digital power manufacturing tool also has a GUI, which helps program the digital parts in the manufacturing environment. You can write and edit programming scripts, which are step-by-step instructions for each digital part. You can also load existing scripts and run these scripts in one-click. The manufacturing GUI is able to program multiple devices in one-click, which is suitable for factory automation, especially in the In-Circuit Test (ICT) phase.

In the following design example, four TPS40425 devices are used in the system to generate three rails (0.9V/90A, 1V/30A and 0.85V/120A). Two TPS40425 devices on address 29 and 30 are configured as three-phase and one-phase for 0.9V/90A and 1V/30A. The other two devices on address 37 and 38 are configured as four-phase for 0.85V/120A.

Note that this tutorial uses system file format to demonstrate the easy to use and easy to program feature of both tools. Other formats of this tool are available including a project file format

Step 1.1 Start Fusion design offline version and create a new system. If opening an existing system, proceed to Step 1.6.

 Step 1.2 Select a device from the list.

 Step 1.3 Pick TPS40425 from one of the four configurations. (MASTER/SLAVE, MASTER/SLAVE)

Step 1.4  Add the first device as Master-Slave, the second device as Slave-Master, the third as Master-Slave and the fourth as Slave-Slave. Modify selected address to 29, 30, 37 and 38.

 Step 1.5 Finish the selections.

Step 1.6 Configure both channels of each device, such as current limit and turn-on delay.

Do not forget to write to hardware or write to all TPS40425 devices. To calculate the OV/UV/PG threshold, VOUT nominal value is needed.

Step 1.7 Set advanced SYNC function.