JAJSS39A November 2023 – March 2024 DAC39RF10EF , DAC39RFS10EF
PRODUCTION DATA
Many systems required synchronization between DAC channels including the phase of the internal NCOs when using digital up-conversion features. Further, frequency hopping systems may have additional requirements for synchronized frequency hopping to maintain NCO synchronization during changes in NCO frequency. The device has a number of ways to update NCO changes. These include:
Update on the rising edge of FRCS of the FRI interface if the FRS bit is set.
The method used for NCO synchronization is controlled through the register setting.
The JESD204C LSB approach allows the synchronization information to be embedded in the input data and can therefore be easily controlled by the data source (that is, FPGA). By controlling the timing of the synchronization bit across multiple devices, multi-device synchronization can be achieved.
Synchronization by issuing a SYSREF pulse requires a DC coupled SYSREF interface and the ability to issue a single SYSREF pulse unless the NCO frequency is an integer multiple of the SYSREF frequency. Many systems will use AC coupled SYSREF signals which eliminates the ability to reliably issue a single SYSREF pulse. Careful timing of the SPI interface, especially for very slow SYSREF signals (< 10 MHz), may make masking and unmasking of SYSREF at multiple devices possible, however it is not characterized since the SPI path is asynchronous.
With SPI_SYNC synchronization, all NCOs within the device can be updated simultaneously.