1.4.2 Holdover Exit Bandwidth
In additional to the Loop and Fastlock bandwidths, a user-selectable bandwidth is available when exiting holdover and locking or
relocking to an input clock when ramping is disabled (HOLD_RAMP_BYP = 1). CBPro sets this value equal to the Loop bandwidth by
default. Note that the BW_UPDATE bit will latch new values for Loop, Fastlock, and Holdover bandwidths simultaneously.
Table 1.4. DSPLL Holdover Exit Bandwidth Registers
Register Name
Hex Address
[Bit Field]
Function
HOLDEXIT_BW
0x059D[5:0]–0x05A2[5:0]
Determines the Holdover Exit BW for
the DSPLL. Parameters are generated by
ClockBuilder Pro.
1.5 Dividers Overview
There are four divider classes within the Si5386.
Figure 1.1 Si5386 Block Diagram on page 7
shows all of these dividers. All divider
values for the Si5386 may be either Fractional or Integer. For best phase noise performance, integer dividers are preferred.
• P0-P3: Input clock wide range dividers (0x0208–0x022F)
• 48-bit numerator, 32-bit denominator
• Min. value is 1; Max. value is 2
24
(Fractional-P divisors must be > 5)
• Practical range limited by phase detector and VCO range
• Each divider has an update bit that must be written to cause a newly written divider value to take effect.
• Soft Reset All will also update the P divider values
• M: DSPLL feedback divider (0x0515–0x051F)
• 56-bit numerator, 32-bit denominator
• Max. value is 2
24
(Fractional-M divisors must be > 10)
• Practical range limited by phase detector and VCO range
• The M divider has an update bit that must be written to cause a newly written divider value to take effect.
• Soft Reset will also update M divider values.
• The DSPLL includes an additional divide-by-5 in the feedback path. Manually calculated M divider register values must be
adjusted accordingly.
• N: Output divider (0x0302-0x0338)
• 44-bit numerator, 32-bit denominator
• Min. value is 5, Max. value is 2
24
(Fractional-N divisors must be > 10)
• Each N divider has an update bit that must be written to cause a newly written divider value to take effect.
• Soft Reset will also update N divider values.
• R: Final output divider (0x0247-0x026A)
• 24-bit field
• Min. value is 2, Max. value is 2
25
-2
• Only even integer divide values: 2,4,6, etc.
• R Divisor=2 x (Field +1). For example, Field=3 gives an R divisor of 8.
Si5386 Rev. E Reference Manual • Functional Description
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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Rev. 1.2 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • December 9, 2021
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