drvxy_MODE
Driver Mode
13
Reserved
14
Reserved
15
Reserved
6.5 Programming for Frequency Select Operations
Every
hsdiv
and
id
has a Bank A and a Bank B divider. The register field names that begin with
hsdivxb
or
idxb
denote Bank B
dividers. Any FS frequency will be:
Foutxy
FS
=
vcoFreq
idxb
Or
Foutxy
FS
=
vcoFreq
hsdivb
Any output associated with either
idxa
or
hsdivxa
can be switched into the above FS frequency. The control that selects the Bank B
divider is as shown in table below.
Table 6.9. The Control Register Bit to Switch Frequencies
Register Field
Description
hsdivx_div_sel
Selects bank A or bank B divider HSDIV0 settings. The HSDIV0 supports dynamic integer divider
changes through this divider select control bit.
0 = bank A divider
1 = bank B divider
idx_cfg_sel
Output interpolative divider 0 configuration bank select. The interpolative divider supports dynami-
cally switching between two complete configurations controlled by this bit. Reconfiguration should
be done on the unselected bank. If ID0_CFG=0, running based off bank A, then bank B may
be freely reconfigured and once ready all changes will be applied to the ID once ID0_CFG=1
thus changing the ID from bank A to bank B. Spread spectrum enable fields ID0A_SS_ENA and
ID0B_SS_ENA are the only exception and may be enabled/disabled while bank is selected.
0 = bank A
1 = bank B
In a factory-programmed part, a pin (the FS pin) can be used for the same purpose as the control registers. Once a control bit is set, the
backup divider values control the output frequency and that is described by the equations below:
For O-Divider
hsdivxb
_
div
=
vcoFreq
Foutxb × Rxa
For N-Divider
idxb
=
vcoFreq
Foutxb × Rxa
The
ida
fraction is represented in register fields IDPB_INTG, IDPB_RES and IDPB_DEN
IDxB
_
INTG
=
floor
(
128 × vcoFreq
Foutxb × Rxa
)
IDxB_RES
IDxB_DEN
= (
128 × vcoFreq
Foutxb × Rxa
) -
IDxB
_
INTG
As can be seen from the equations above, the backup divider values limit the possible values for the output frequency in this backup
mode. Another key feature is that the switch to a FS frequency is “glitchless”. Therefore, the recommended method for glitchless
frequency updates is to program either divider a or b (when divider b or a is currently driving the output frequency), and then switch this
divider.
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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