In production test, optimization of one test can degrade another test that must be performed on the same device. By contrast, in bench testing, you can employ one set of instruments to measure one parameter and then decide to use different equipment to measure another. In production testing, the extra interface circuit needed for this test will compromise the noise performance. Overcoming this condition requires improvements in both the quality of the test signal into and out of the device and the stability of the test clock. At Teradyne, we developed an approach for optimizing signal quality by stabilizing the clock when testing high-speed ADCs.
Test equipment can be a significant source of noise.
This ADC test interface can evaluate ADC parameters such as noise, offset, linearity, and distortion. As a result, the tester cannot be built in a single compact unit. The sine waves generated by the VHF source instruments were filtered by a narrow bandpass filter to produce as perfect a test signal as possible. Fourier analysis of a captured signal provides information on the fundamental power as well as on the harmonics and all other unwanted components. From the Fourier analysis of Figure 3a, you can see that the bandpass filter reduces the noise outside of its passband.