ZHCSIA3C Februray 2017 – May 2018 LMK04832
PRODUCTION DATA.
By programming MAN_DAC_EN = 0 and TRACK_EN = 1, the tracked voltage of CPout1 is set on the CPout1 pin during holdover. When the DAC has acquired the current CPout1 voltage, the DAC_Locked signal is set which may be observed on Status_LD1 or Status_LD2 pins by programming PLL1_LD_MUX or PLL2_LD_MUX, respectively.
Updates to the DAC value for the Tracked CPout1 sub-mode occurs at the rate of the PLL1 phase detector frequency divided by (DAC_CLK_MULT × DAC_CLK_CNTR).
The DAC update rate should be programmed for ≤ 100 kHz to ensure DAC holdover accuracy.
The ability to program slow DAC update rates, for example one DAC update per 4.08 seconds when using 1024-kHz PLL1 phase detector frequency with DAC_CLK_MULT = 16,384 and DAC_CLK_CNTR = 255, allows the device to look-back and set CPout1 at a previous good CPout1 tuning voltage values before the event which caused holdover to occur.
The current voltage of DAC value can be read back using RB_DAC_VALUE, see RB_DAC_VALUE.