In today's electronic products, the signal speed is getting faster and faster, and the power supply voltage of integrated circuit chips is getting smaller and smaller. In the 1990s, the power supply of chips is usually 5V and 3.3v, but now, the power supply of high-speed IC is usually 2.5v, 1.8v or 1.5v, etc. For this kind of low voltage dc power supply voltage test (referred to as power source noise test), this paper will briefly discuss and analyze.
In power source noise test, there are usually three problems that lead to inaccurate measurement
Quantization error of oscilloscope
Use a probe with a large attenuation factor to measure small voltages
The distance between GND and signal of probe is too large
Oscilloscope, quantitative error exists real-time oscilloscope ADC for eight, of the analog signal is transformed into quantitative level (i.e., 256), when constitute only a small part of the screen, the wave form of quantization interval, reduced the precision, accurate measurement need to adjust the vertical scale of oscilloscope (using variable gain when necessary), as far as possible let waveform fill the screen, make full use of the vertical dynamic range of the ADC.