3.1.1 Dividers
There are five main divider classes within the Si5397/96. Additionally, FSTEPW can be used to adjust the nominal output frequency in
DCO mode. See Section
7. Digitally-Controlled Oscillator (DCO) Mode
for more information and block diagrams on DCO mode.
• 1. PXAXB: Reference input divider (0x0206)
• Divide reference clock by 1, 2, 4, or 8 to obtain an internal reference < 125 MHz
• 2. P0-P3: Input clock wide range dividers (0x0208-0x022F)
• Integer or Fractional divide values
• Min. value is 1, Max. value is 2
24
(Fractional-P divisors must be > 5)
• 48-bit numerator, 32-bit denominator
• Practical P divider range of (Fin / 2 MHz) < P < (Fin / 8 kHz)
• Each P divider has a separate update bit for the new divider value to take effect
• 3. MA-MD: DSPLL feedback dividers (0x0415-0x041F, 0x0515-0x051F, 0x0615-0x061F, 0x0716-0x0720)
• Integer or Fractional divide values
• Min. value is 1, Max. value is 2
24
(Fractional-M divisors must be > 10)
• 56-bit numerator, 32-bit denominator
• Practical M divider range of (Fdco / 2 MHz) < M < (Fdco / 8 kHz)
• Each M divider has a separate update bit for the new divider value to take effect
• Soft reset will also update M divider values
• 4. Output N dividers N0-N3(0x0302-0x032D)
• MultiSynth divider
• Integer or fractional divide values
• 44 bit numerator, 32 bit denominator
• Each divider has an update bit that must be written to cause a newly written divider value to take effect.
• 5. R0-R7: Output dividers (0x024A-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
• FSTEPW: DSPLL DCO step words (0x0423-0x0429, 0x0523-0x0529, 0x0623-0x0629, 0x0724-0x072A)
• Positive Integers, where FINC/FDEC select direction
• Min. value is 0, Max. value is 2
24
• 56-bit step size, relative to 32-bit M denominator
Si5397/96 Reference Manual
Functional Description
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