The table below shows the register fields (and terms)
idxy_ss_step_num
and
idxy_ss_step_res
.
idxy_ss_step_num
is the number of
frequency steps between the mean and the maximum/minimum frequencies in SSC clocking and
idxy_ss_step_res
is the frequency
resolution that is required in each step. The goal is to maximize the number of steps and minimize the resolution. However, the number
of steps is set by the modulation rate (typically 30–33 kHz). The step resolution can be minimized by setting the largest value possible
for
idxy_den
.
Idxy_den
is the denominator of the
id
divider and setting it as close as possible to 2
15
– 1 is desired.
Table 6.10. SSC Register Fields
idxy_ss_ena
Spread spectrum enable. This is the only bank configuration field which may be changed dynamical-
ly while the bank is selected as the active bank. Users may freely enable/disable spread spectrum.
0 = spread spectrum disabled
1 = spread spectrum enabled
idxy_ss_mode
Spread spectrum mode.
0 = disabled
1 = center
2 = invalid
3 = down
idxy_ss_clk_num
Number of output clocks for each frequency step.
idxy_ss_step_num
Number of frequency steps in one quarter SSC modulation period, allows for frequency step every
output clock.
idxy_ss_step_intg
Divide ratio spread step size.
idxy_ss_step_res
Numerator of spread step size error term.
idxy_ss_step_den
Denominator of spread step size error term.
To enable SSC,
idxy_ss_ena
needs to be set and the right mode selected in
idxy_ss_mode
. The number of output clocks in each
frequency step,
idxy_ss_clk_num
, needs to be set to 1 and
idxy_ss_step_den
is the same as
idxy_den
and
idxy_ss_step_intg
is
always zero.
The following flow needs to be followed to program the registers into Si5332:
1. Write 0x01h to register 0x06h and put the Si5332 into the READY state.
2. Write all the relevant registers as calculated from the steps above.
3. Ensure that the valid input clocks are available for the Si5332 to attempt a PLL lock.
4. Write 0x02h to register 0x06h and put the Si5332 into the ACTIVE state.
Si5332-AM1/2/3 Automotive Grade Device Reference Manual • Programming the Volatile Memory (Registers)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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Rev. 0.3 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 26, 2021
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