Copyright © 2020
Alazar Technologies Inc.
ATS9353 User Manual
49
External Clock
The ATS9353 PCI Express Digitizer allows you to bypass the on-board clock
oscillator and supply your ADC clock. This feature is extremely important in
many RF applications in which phase measurements must be made between the
inputs themselves or between the inputs and an external event.
Another application that requires external clock is Optical Coherence
Tomography (OCT) that sometimes requires analog sampling to take place
relative to an MZI clock, sometimes also known as k-clock.
Driving high performance ADCs must be done carefully, as any injection of
phase jitter through ADC clocks will result in reduction in data conversion
quality.
Aside from phase noise, the clock signal for a pipelined ADC must also have a
duty cycle close to 50%. This maximizes the dynamic performance of the ADC.
See Fast External Clock section below for more details.
External clock input impedance is fixed at 50
Ω
.
External clock input is always AC-coupled.
There are two types of External Clock supported by ATS9353:
•
Fast External Clock
•
10 MHz Clock Reference
The following paragraphs describe the two types of External Clock input and
outline the restrictions on each of them.