Posted on: July 1, 2014
What is Margining?
Adjusting a power supply output voltage up or down from its minimal setting in order to verify system performance margin with respect to supply voltage. This is usually done electrically by a system-generated control signal.
The margining process is one of the two concepts of testing load behavior at the power supply margins. Depending on the specified voltage range of the system or equipment, the power supply output voltage is adjusted and the system response observed at these margins.
Manufacturers of various high reliability systems are required to test their products strenuously before releasing them into the market. The margining test is usually performed once, and carried out at the manufacturer’s test lab.
Power supplies as well as electrical equipment, are usually designed to operate with some tolerances of say ±5%, ±10%. The margining process allows the power supply to be adjusted to the low-end and high-end of the tolerance range as tests are performed to ensure that the load still operates correctly.
Voltage margining evaluates the load circuit ability to tolerate variations in the power supply voltage which may arise from various factors based on time, temperature, fluctuations in input voltage or other factors.
The process dynamically tests the load circuit over its specified supply voltage range and allows for the evaluation of the ability of the equipment’s circuit to tolerate changes in power at the extremes specified by the manufacturer.
During the test, the supply output voltages are adjusted and then the electrical components of the load tested at both the lower and upper voltage limits as specified in the design.
To carry out the margining test, a centralized power management device is used. This has a supply-adjustment capability that allows the margining test to be carried out without having to add extra components or redesigning the PCB area.
There are several integrated circuits from different manufacturers which are to perform the voltage adjustments required for the margining test. The margining controller ICs enables the precise adjustments of the output voltage of the power supply and allows the scaling of the output voltage to cover the desired range of say ±5%, ±10% depending on the equipment under test.
A voltage adjust pin, sourcing or sinking current into the power supply feedback node, are the common methods that are used to adjust the output voltage either upwards or downwards as desired.
The margining controllers have different capabilities and the choice is dependent on requirements. Whiles some will only perform adjustment on only one voltage rail; there are others which can adjust several rails simultaneously.
The margining test helps in evaluating an electronics equipment’s performance at the power supply voltage limits specified by the manufacturer and are widely used in a variety of high reliability systems. Typical systems include industrial control systems, servers, network storage systems, telecom, cellular infrastructure, Internet-routing and switching systems, set-top boxes, notebook PCs, automotive, and more.