Measuring the timing jitter of ATE in the frequency domain

The objective of this paper is to provide a framework by which jitter, in the output signals of a test-head board in an automatic test equipment (ATE), can be measured. In this paper, jitter phenomena caused by radiated electromagnetic interference (EMI) noise are considered. EMI noise is mainly present in the test head of an ATE as result of the activity of the dc-dc converters. An analysis has been pursued to establish the areas of the test-head board that are most sensitive to EMI noise. The most sensitive part of the test-head board has been found to occur in the loop filter of the phase-locked loop (PLL) that is used to obtain a high-frequency clock for the timing generator (TG). Different H-fields are then externally applied to the loop filter to verify the behavior of the output signal in terms of rms jitter. A frequency-domain methodology has been employed for the rms-jitter measurements. The rms-jitter variation for the radiated EMI magnitude and frequency has been characterized. Also, the orientation of the external H-field source has been investigated with respect to the target board and its effects on the measured rms jitter. For measuring the jitter, an interface circuitry has been designed on an adapter board to circumvent ground noise and connectivity problems arising from the test-head environment.