SI5380 Datasheet, PDF (19/50 Pages) Silicon Laboratories – Ultra-Low Phase Noise, 12-output JESD204B Clock Generator

Si5380 Data Sheet
Functional Description
3.5.15 Output Skew Control (Δt₀ - Δt₄)
The Si5380 uses independent dividers (N0 - N4) to generate up to 5 unique frequencies to its 12 outputs through a crosspoint switch. A
delay path (Dt0 - Dt4) associated with each of these dividers is available for applications that need a specific output skew configuration.
This is useful for compensating PCB trace delay differences or for applications that require quadrature clock generation. The resolution
of the phase adjustment is approximately 68 ps per step up to 128 steps of added phase delay (+8.6 ns late), or 128 steps of negative
delay (–8.6 ns early). Phase adjustments are register configurable. An example of generating two frequencies with unique configurable
path delays is shown in the following figure.
÷N0 t0
÷N1 t1
÷N2 t2
÷N3 t3
÷N4 t4
÷R0A
÷R0
÷R1
÷R2
÷R3
÷R4
÷R5
÷R6
÷R7
÷R8
VDDO0
OUT0A
OUT0Ab
OUT0
OUT0b
VDDO1
OUT1
OUT1b
VDDO2
OUT2
OUT2b
VDDO3
OUT3
OUT3b
VDDO4
OUT4
OUT4b
VDDO5
OUT5
OUT5b
VDDO6
OUT6
OUT6b
VDDO7
OUT7
OUT7b
VDDO8
OUT8
OUT8b
÷R9
÷R9A
OUT9
OUT9b
OUT9A
OUT9Ab
VDDO9
Figure 3.16. Example of Independently Configurable Path Delays
All phase delay values are restored to their default values after power-up, power-on reset, or hardware reset using the RSTb pin. Phase
delay default values can be written to NVM allowing a custom phase offset configuration at power-up or after power-on reset, or after a
hardware reset using the RSTb pin.
3.5.16 Output Divider (R) Synchronization
All the output R dividers are reset to a known state during the power-up initialization period. This ensures consistent and repeatable
phase alignment across all output drivers. Resetting the device using the RSTb pin or asserting the reset bit will have the same result.
Asserting the sync register bit provides another method of realigning the R dividers without resetting the device.
3.6 Power Management
Unused inputs and output drivers can be powered down when unused. Consult the Si5380 Reference Manual and ClockBuilder Pro
configuration utility for details.
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