3.3 Measuring Jitter and Phase Noise
For jitter and phase noise measurements, buffered output configuration is recommended. SiTime OCXO
was not designed to drive 50 Ω load directly so buffer avoids excessive current draw from the device
output. For minimal impact on the measurement LMK1C1104 low-additive jitter buffer is used on the board.
SMA connector is used to connect directly to the jitter measurement instrument, such as Time Interval
Analyzer (TIA) or high-bandwidth real-time oscilloscope. Jitter measurement technique is described in
SiTime AN10007.
The SMA can also be connected through 50 Ω coaxial cable to signal source analyzers or spectrum
analyzers to measure phase noise. In such case the use of AC-coupling configuration is recommended
because not all measurement instruments can accept DC voltage at their inputs.
3.4 Current Measurement
To measure the current consumption user, need to use ammeter/multi-meter in the power supply
circuit. We recommend removing diode D1 to avoid measuring the additional current of the diode
circuit. It is recommended to measure the voltage on DUT VDD and adjust for any drop on the DMM to
ensure known VDD voltage on the device. VDD adjustment must be completed before every current
measurement.
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