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Home > News > Company News > Avoid the power management bli.....

Avoid the power management blind spots

  • Author:Ella Cai
  • Release on:2017-07-13
Bruce Haug explains how to avoid voltage rail blind-spots in digital power management.

Knowing the condition and operating status of a voltage regulator is perhaps the last remaining blind-spot in modern electronic systems, since they do not normally have the means to directly configure or remotely monitor key operating parameters. 

The regulator’s status is usually critical for reliable operation when regulator output voltage drifts, or during an over temperature condition; these must be detected and acted upon before a potential failure event occurs. 

Digital power system management (DPSM) can simplify and accelerate system characterisation, optimisation and data mining during prototyping, deployment and field operation. 

A DPSM approach to such systems allows engineers to monitor the performance of a voltage regulator and report back on its health so that corrective action can be taken before it goes out of specification, or before failure. DPSM allows users to act on the information collected from the load and the system. 

Digital control of analogue power supplies with a simple PC connection is especially valuable during the development stage, to get systems up and running quickly. There can be as many as 50 point-of-load (POL) voltage rails on some boards and the system designer needs to be able to quickly and easily monitor and adjust supply voltages, sequence supplies up/down, set operating voltage limits and read parameters such as voltage, current and temperature as well as access detailed fault-logging. 

High accuracy is extremely important in these systems to maintain tight control over the rails while achieving maximum performance. 

DPSM is rapidly being adopted in many systems because of its ability to provide accurate information about the power system and its ability to autonomously control and supervise many voltages. 

Linear Technology has several digital power products that enable this level of functionality, for example the recently-released LTC3886, a 60V input dual-output synchronous step-down DPSM controller that can produce an output voltage up to 13.8V. 

The LTC3886’s two-wire serial interface allows outputs to be margined, tuned and ramped up or down at programmable slew rates with sequencing delay times. This interface provides a means for DPSM products to seamlessly integrate with existing embedded systems and architectures, board‑mount controllers (BMCs) and intelligent platform management interface (IPMI) functions. 

For ease of use, especially at the earliest stages of hardware development and testing, it is common to interact with DPSM devices through a GUI running on a PC and through a USB-to-PMBus communications converter tool (dongle). The GUI can provide control and monitoring of key operating parameters such as power consumption, voltages, sequencing, margining, and even fault log records. 

Since it is not uncommon for a system board to have 50 or more power rails, these types of boards are usually densely populated, so the DPSM circuitry cannot take up too much space. Furthermore, it must be easy to use and be able to control a high number of rails. Such products must operate autonomously or communicate with a system host processor for command, control and to report telemetry information. 

DPSM creates a tool for system designers to control power supplies with a simple PC connection and digital interface. This capability is valuable during the development and debug stage, enabling designers to get their systems up and running quickly with the ability to control and adjust supply voltages, limits and sequencing. Margin testing is easier since the entire test can be controlled by a couple of commands over an I²C/PMBus. 

DPSM provides the user with power consumption data, allowing for smart energy management decisions to be made, which can reduce overall power consumption. Power system data about the power supplies’ health can be sent back to the OEM, effectively opening up the blind-spot with regards to DC-DC converters. 

A regulator’s output voltage drift over time or an over temperature condition can be detected and acted upon before a potential failure event occurs. 

If a board is returned, the fault log can be read back to determine which fault occurred, the board temperature and the time at which the fault happened. This data can be used to quickly determine the root cause, or if the system was operated outside of its specified operating limits or to improve the design of future products. For high rail-count systems and OEMs that want to avoid voltage rail blind-spots, digital power system management is a powerful tool. 

How DPSM helps 

To speed time-to-market you can:
change power parameters without re-spinning the PCB
perform quick system characterisation, optimisation and data mining.
Load-level benefits give:
control of power supply accuracy over time and temperature
margining to test FPGA tolerance
efficiency boost by load shedding. 

System-level benefits are:
it provides digital access to board‑level power diagnostics
you can monitor and pinpoint system‑wide power consumption
you can manage/log faults. 

Deployment benefits:
it helps to monitor power consumption trends and detect fluctuations/changes over time
you can develop predictive analytics to cut operating costs
and decide energy management.