ZHCSFU8B May 2016 – December 2021 ADC32RF80 , ADC32RF83
PRODUCTION DATA
When SYSREF is a periodic signal, its frequency is required to be a sub-harmonic of the internal local multi-frame clock (LMFC) frequency, as described in Equation 1. The LMFC frequency is determined by the selected decimation, frames per multi-frame setting (K), samples per frame (S), and device input clock frequency.
where
In order for the interleaving correction engine to synchronize properly, the SYSREF frequency must also be a multiple of fS / 64. Table 8-2 provides a summary of the valid LMFC clock settings.
OPERATING MODE | LMFS SETTING | LMFC CLOCK FREQUENCY | SYSREF FRQUENCY |
---|---|---|---|
Decimation | Various | fS(1) / (D × S(4) × K(3)) | fS / (N × LCM(2) (64, D(5) × S × K)) |
The SYSREF signal is recommended to be a low-frequency signal less than 5 MHz in order to reduce coupling to the signal path both on the printed circuit board (PCB) as well as internal to the device.
Example: fS = 2949.12 MSPS, Divide-by-4 (LMFS = 8411), K = 16
SYSREF = 2949.12 MSPS / LCM (4 ,64, 16) = 46.08 MHz / N
Operate SYSREF at 2.88 MHz (effectively divide-by-1024, N = 16)
For proper device operation, disable the SYSREF signal after the JESD synchronization is established.