The operating voltages of semiconductor devices are gradually being lowered as a countermeasure to the growing power requirements of increasingly high-performance devices and to reduce environmental impact. As a result, noise margins are also decreasing and semiconductor devices are becoming increasingly susceptible to electrical noise.
The types of electrical noise that affect the operation of semiconductor devices include the following:
Power supply noise
Simultaneous switching noise
An enormous number of transistors repeatedly turn on and off (switching) in a semiconductor device. Generally, the switch timing differs from one transistor to another. However, a large number of transistors switching at the same time will cause a substantial change in the potential of the power supply or ground voltage, induce switching noise, and increase the possibility of device malfunction.
This type of noise is generated as the result of signal lines that run in parallel influencing one another. The closer the signal lines are to one another and the longer the distance the signal lines run, the higher the cross-talk noise, which can cause the device to malfunction.
Semiconductor devices are composed of chips, wires, through-holes and various other elements, each of which has its own characteristic impedance. Signal reflection noise is generated at the boundary surface where two elements with different characteristic impedances meet, and may cause device malfunction.
This is a phenomenon whereby the waveform of a signal flowing through a circuit gradually becomes unclear due to resistance or other influences. The higher the frequency of the signal, the greater the attenuation. Attenuation is a serious problem particularly at frequencies above 1 GHz.
Jitter is the deviation of a digital signal due to reflection or some other cause. In a digital circuit, signal transmission is synchronized with the timing of a clock signal generated by a crystal oscillator, etc.; however, jitter may disturb this timing, causing the circuit to malfunction.