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Keysight Technologies
Testing Circuit Board Power Distribution
Using Real World Distortions
Application Note
Introduction
The Role of a Pulse Function Arbitrary
Noise Generator in Stress Test Applications
Situation analysis
In this digital era, embedded design engineers are using integrated circuits (ICs) to solve electronic
challenges. Populated on printed circuit boards (PCBs), the ICs typically receive power from a central
supply. With each IC used, its impact on electrical power must be considered. Most ICs draw current
only when changing electrical states and this irregular power use introduces distortions to the power
supply network.
Such signal distortions potentially interfere with other circuits and raise the electrical noise level.
This leads to reduced signal-to-noise ratios and affects the signal integrity on the outputs of the
ICs. In a worst case scenario, noise can negatively affect the operation of the IC. Fluctuating
voltage levels can interfere with correct IC operation as well.
To limit the effect of these irregularities, hardware engineers use an array of protective circuits.
Common methods to safeguard ICs include using a decoupling capacitor to counter voltage
luctuation, and incorporating an inductor to limit the noise level. Unfortunately, every compen-
sation method used to minimize power distortions at the circuit has its limitations.
For example, consider the use of a decoupling capacitor. Material imperfections within the
capacitor lead to equivalent serial resistance. Capacitor and packaging lead to equivalent serial
inductance. These parasitic effects negatively inluence the capacitor's technical characteristics.
At high frequencies the capacitor behaves more like an inductor or resistor--defeating its original
purpose in the circuitry.
Solution Coniguration Testing components and compensation circuits under real-world conditions
is essential. It is this process that allows engineers to assess the PCB's
design and power consumption. Testing also provides engineers with the
insight necessary to enhance the device's overall performance.
Figure 1 illustrates an effective method for simulating real-world conditions
during the design stages. The components of this solution are summarized
in Table 1.
Oscilloscope Oscilloscope
L OUT0 OUT1
VCC
DC power supply TP1 TP2
IC
C
GND
Pulse function arbitrary noise
generator 81150A or 81160A
Figure 1. Test setup for simulating real-world conditions
Table 1. Test equipment to simulate real-world conditions
Device Type Keysight Solution
DC power supply E3631A 80W triple output power supply, 6 V, 5 A, and