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- Software-selectable decimation factor (1 to 100,000) for Fast External Clock and 10 MHz Reference Clock
- 50 Ohm input impedance for AC signals
- 10 kiloOhm input impedance for DC
ATST146: External Clock Upgrade
While the ATST146 features a 10 MHz TCXO as the source of the timebase system, there may be occasions when digitizing has to be synchronized to an external clock source. ATST146 External Clock option provides an SMA input for an external clock signal with a frequency between 125 MHz and 1 MHz.
Users can also set a decimation factor for the external clock. For example, if the user wants to digitize the input signal on every tenth clock edge, this factor can be set to 10. Minimum decimation value is 1 and maximum is 100,000.
There are three supported types of External Clock
- Fast External Clock
A new sample is taken by the on-board ADCs for each rising (or falling) edge of this External Clock signal. Fast External Clock frequency must always be higher than 1 MHz and lower than 125 MHz in order to satisfy the clocking requirements of the ADC chips being used. - Slow External Clock
This type of clock should be used when the clock frequency is either too slow or is a burst-type clock. In this mode, the ATST146 ADCs are run at a preset internal clock frequency. The user-supplied Slow External Clock signal is then monitored for low-to-high transitions. Each time there is such a transition, a new sample is stored into the onboard memory. - 10 MHz Reference Clock
It is possible to generate the sampling clock based on an external 10 MHz reference input. ATST146 uses an advanced clock generator circuit consisting of a VCO and PLL to generate the sampling clock.