Milli Ohm Measurements - Know how to Use Milli-ohm Meters Correctly
Processor power distribution network plays an important role in the proper working of a processor. A PDN is designed based on the impedance versus frequency characteristics. PDN design starts with the assessment of target impedance which is the ratio of maximum change is allowed voltage to the maximum change in current. The maximum change in current is usually taken as half the input current to a processor. To avoid ringing on the PDN, it is important to design the PDN as flat as possible. This reduces the radiated EMI issues. This also helps to improve the eye diagram for a transceiver chip. The most important issue in designing in the PDN is in measuring the PDN impedance. Current industry standard chips are designed at the milli ohm impedance levels, and measuring impedance at these levels are a challenge. High end processors are designed with micro ohm impedance levels. Another challenge is that they have to measured at the highest frequency of interest – usually ...