The following is a Category 1 SYNC configuration, because:

• M = 1 (Doubler and MULT are not used)
• f_OUT is an integer multiple of f_OSCIN (6000 / 100 = 60)
• Channel divider is bypassed (output frequency = VCO frequency)

With this configuration, the outputs are in phase after programming the LMX2820 devices. The output phases remain constant if:

• LMX2820 is powered down and powered up again
• VCO is calibrated again
• LMX2820 is reset and re-programmed

Figure 3-4 Category 1 SYNC Result

Below is another Category 1 SYNC configuration example. This configuration has enabled the Doubler:

• M = 2 (Doubler is enabled)
• Channel divider is bypassed
• f_OUT is an integer multiple of M × f_OSCIN (6000 / 200 = 30)
• PLL_NUM = 0

If only one of the LMX2820 devices has the Doubler enabled, although both configurations are Category 1 SYNC, the Doubler introduces addition delay in the input path. This delay is carried forward to the output. As a consequence, the phases of the LMX2820 outputs are not exactly in phase. To get exact phase match between multiple LMX2820 devices, the configurations should be identical.

Figure 3-6 Phase Offset Due to Unsymmetrical Configuration