SNAS751 December 2023 LMK5C33414A
PRODUCTION DATA
The phase valid monitor is designed specifically for 1-PPS input validation because the frequency and window detectors do not support this low frequency. The phase valid monitor uses a window detector to validate 1-PPS input pulses that arrive within the nominal clock period (TIN) plus a programmable jitter threshold (TJIT). When the input pulse arrives within the counter window (TV), the pulse is considered valid and the phase valid flag is cleared. When the input pulse does not arrive before TV (due to a missing or late pulse), the flag is set immediately to disqualify the input. TJIT should be set higher than the worst-case input cycle-to-cycle jitter.
The phase valid register settings also are valid for 1-PPS ppm error threshold detect. Notice the TJIT also impacts the worst case ppm error allowed. For example: High_Jitter_Freq = 1/(TIN - TJIT), then Max input allowable ppm error = (High_Jitter_Freq - Expected_Freq) / Expected_Freq × 1e6.