JAJSHR5A January 2015 – August 2019 ADS54J54
PRODUCTION DATA.
Periodic: The SYSREF signal is always on. This mode is supported, but not recommended as the continuous SYSREF signal appears like an additional clock input, which can cause clock mixing spurs in the channel output spectrum.
Gapped-Periodic (recommended): A periodic SYSREF signal is presented to the ADS54J54 SYSREF inputs for a very short period of time. This configuration requires a DC-coupled SYSREF connection for proper operation. Most of the time the SYSREF signal is in a logic-low state, and thus cannot cause any glitches and spurs in the channel output spectrum.
Pulse/One Shot (recommended): A single SYSREF reset pulse is used to synchronize the ADS54J54. The ADS54J54 device requires a minimum of 3 SYSREF pulses to complete the synchronization phase. The SYSREF signal is in a logic-low state most of the time, and thus cannot cause any glitches and spurs in the channel output spectrum. Special attention should be given to ensure the single pulse meets required the SYSREF input setup and hold time.