Step-Down DC/DC Controllers Employ PMBus Functions to Enhance System Performance

Mar 1, 2011 12:00 PM
Sam Davis, Editor-in-Chief, PET

Find a downloadable version of this story in pdf format at the end of the story.

THE POWER Management Bus (PMBus) will finally do what its developers always intended it to do: manage and monitor the operation of a dc-dc converter. These capabilities are integrated into Linear Technology Corporation's LTC3880 and LTC3880-1 that are dual output, high efficiency synchronous step-down DC/DC controller ICs with an I²C-based PMBus interface for digital power management. The ICs combine an analog switching regulator with precision mixed signal data conversion to provide power system design, management, and monitoring.

By using the PMBus functions, multiple designs can be easily calibrated and configured in firmware to optimize a single hardware design for a range of applications. The converter loop gain does not change if the power supply parameters are modified, so compensation remains optimized for multiple configurations. Products best served by these PMBus functions include high current power supplies employed in telecom, datacom, computing and storage systems. For more information on PMBus, see the box titled “Power Management Bus (PMBus)”.

PMBUS IN ACTION

The LTC3880/-1 allows digital programming and read back for real-time control and monitoring of critical point-of-load converter functions. Configurations are saved to internal EEPROM over the device's I²C serial interface supported by Linear Technology's LTpowerPlay GUI-based development software. With configurations stored on-chip, the controller powers up autonomously without burdening the host processor.

PMBus functions include the ability to program specific power supply management parameters, including:

Related Articles

Power Management Bus (PMBUS) As explained by the Power Management Bus Implementer's Forum, The Power Management Bus (PMBus) is an open standard power-management protocol with a fully...

• Output Voltage
• Input Voltage
• Current Limit
• Switching Frequency
• Overvoltage and undervoltage
• On and Off Delay Times
• Output Rise/Fall Times

In addition, PMBus functions include the ability to monitor power supply operation, including:

• Internal Controller Temperature
• External System Temperature
• PWM Duty Cycle
• Output Current
• Output Voltage
• Input Voltage
• Input Current

Plus, there is also the ability to shutdown power supply operation by allowing all faults to be individually masked with operation in either unlatched (hiccup) or latched modes. Individual status commands enable fault reporting over the I²C serial bus to notify the host processor of the specific fault event, including:

• Internal/external overtemperature
• Output undervoltage/overvoltage
• Input undervoltage/overvoltage
• Input and output overcurrent
• Communication, memory or logic Fault

Continue on next page

Want to use this article? Click here for options!
© 2007 Penton Media, Inc.