SBAS932 March 2024 DAC39RF10-SEP , DAC39RF10-SP , DAC39RFS10-SEP , DAC39RFS10-SP
PRODMIX
There are two deterministic methods for synchronizing the NCO (frequency or phase change, accumulator reset): through an LSB of the JESD204C interface or via SYSREF. The latency parameters for each sychronization method are listed in Table 7-41.
Using SYSREF as the Synchronization source, the latency parameter TSYSREF_NCO is the time between the moment SYSREF is sampled high by CLK and the arrival of the NCO change at the DAC output. The alignment to the data path samples can be calculated by the Excel spreadsheet latency calculator discussed in Section 7.4.4.
When using the JESD204C interface LSB, the latency parameter TJSYNC_NCO is the difference in time of the NCO synchronization event relative to the corresponding data sample aligned with the LSB. TJSYNC_NCO is deterministic, but for some modes depends on the alignment of the LSB rising edge to the multiframe boundary (see Table 7-42).
Latency Parameter | Description | Value |
---|---|---|
TSYSREF_NCO | Latency from SYSREF sampled high (by CLK) to DAC output reacting to an NCO synchronization event (that was triggered by SYSREF). | 477.5 CLK cycles |
TJSYNC_NCO | The latency through the interpolation filter(s) to the NCO minus the latency of the LSB that synchronizes the NCO. Applies only when using the LSB of the input data to synchronize the NCO. To make input sample n be the first sample to be mixed with a new NCO frequency or phase, the LSB should be brought high on sample n’ = n+TJSYNC_NCO/LT. Note that n’ may not be an integer as the synchronization path is not always a whole number of input sample periods. | See Table 7-42 |
Interpolation Factor (LT) | TJSYNC_NCO [CLK cycles](1) |
---|---|
2 | -144, -142, -140, -138, -136, -134, -132, -130 |
3 | -89, -86, -83, -81, -80, -78, -77, -75, -74, -72, -71, -69, -68, -66, -63, -60 |
4 | -36, -32, -28, -24 |
6 | 34, 40, 42, 46, 48, 52, 54, 60 |
8 | 86, 94 |
12 | 186, 194, 198, 206 |
16 | 290 |
24 | 458, 466 |
32 | 648 |
48 | 968 |
64 | 1396 |
96 | 2036 |
128 | 2932 |
192 | 4212 |
256 | 6004 |