PMBus ICs for Power Supply Design and Telemetry
Bruce Schreiner posted on June 25, 2014 |
Turn your power supply design, configuration, control, and monitoring inside out without increasing ...

For computer design, communications, avionics, or even defense; PMBus IC's can control your power factor corrections, isolated DC/DC conversions, and point-of-load systems.

It is true that Digital power controllers offer designers the maximum level of control to capture telemetric data (in terms of scalability, monitoring data in real-time, and fail condition definitions). However, this set up is expensive, complex and often overkill for many applications. Alternatively, designers can include expensive yet accurate external IC's, like digital-system health monitors to collect telemetry when the accuracy is key to performance. Again, however, this is not always necessary.

PM Bus converters from Texas Instruments (TI), on the other hand, help to simplify the design and offer a middle ground. Though PMBus converters will not have as large of a list of register sets as digital power controllers, it has the ability to work with the key telemetry parameters needed for the control of many designs. PMBus registers that are common for data storage, measurement and system control include:

  • Soft-Start times
  • Output Voltage adjustments and margining
  • Overcurrent protection & setting current limits
  • Under voltage lockout level (V­DD)
  • Frequency switching

Additionally, as TI was a key player in the development of the PMBus open standard power-management protocol, you could say they are well versed in digital power from line to load.

 


PMBus Power System

 

The PMBus open standard is similar to I2C and SMBus. The benefit being that PMBus is more robust, providing additional transport, physical layers, commands, and added interrupt capabilities.  PMBus allows for the communication needed for configuration, control, and monitoring of all aspects of the power supply system between the ICs.  Additionally, once configured the system has a set-and-forget programmed operation that would negate the requirement for a microcontroller.

The TI PMBus portfolio of ICs includes buck converters, system protection, monitoring, point-of-load PWM controllers, and digital PWM controllers with 250 ps resolution. Therefore, TI's portfolio covers virtually all aspects of power supply designs. 

For instance, using the digital information transferred on the PMBus optimization of power density can be achieved by reading the actual current draw. This will in turn improve the reliability while reducing costs based on actual power draw. You can also reduce design time by using PMBus GUI tools and optimizing future designs using the operational data you've just collected. 

Therefore, TI notes that using their PMBUs devices in a design will:

  • Increase power density
  • Increased reliability of power supplies
  • Optimized component performance & efficiency
  • Reduced design time
  • Reduced risk
  • Reduced cost 

 

It appears that using TI PMBus device ICs allows you to design a system with the maximum level of control (digital power controller), or shoot for a simplistic design using PMBus converters (analog power IC) with integrated telemetry. However, if flexibility and accuracy are key you can use an external digital system to monitor the power supply operation.  All of these methods are described in detail in this white paper.

As usual, these PMBus TI ICs are supported by related technical documents, training / user communities, and tools / software.  The Fusion Digital Power Designer GUI configures and monitors TI digital power controllers via a PC USB to serial interface adapter.

TI's PMBus portfolio of ICs allows you to collect control telemetry to turn your power supply designs upside down and inside out with little effort.

Texas Instruments has sponsored promotion of their industrial communications solutions on ENGINEERING.com. They have no editorial input to this post - all opinions are mine.  Bruce Schreiner

     

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