13. Power Management
13.1 Power Management Features
Several unused functions can be powered down to minimize power consumption. The registers listed below are used for powering
down different features.
Table 13.1. Power-Down Registers
Register Name
Hex Address [Bit
Field]
Function
Si5391/Si5391P
PDN
0x001E[0]
This bit allows powering down the device. The serial interface
remains powered during power down mode.
OUT0A_PDN
0x0103[0]
Powers down unused clock outputs.
OUT0_PDN
0x0108[0]
OUT1_PDN
0x010D[0]
OUT2_PDN
0x0112[0]
OUT3_PDN
0x0117[0]
OUT4_PDN
0x011C[0]
OUT5_PDN
0x0121[0]
OUT6_PDN
0x0126[0]
OUT7_PDN
0x012B[0]
OUT8_PDN
0x0130[0]
OUT9_PDN
0x0135[0]
OUT9A_PDN
0x013A[0]
OUT_PDN_ALL
0x0145[0]
Power down all output drivers
XAXB_PDNB
0x090E[1]
0-Power down the oscillator and buffer circuitry at the XA/XB pins
1- No power down
13.2 Power Supply Recommendations
The power supply filtering generally is important for optimal timing performance. The Si5391/Si5391P devices have multiple stages of
on-chip regulation to minimize the impact of board level noise on clock jitter. Following conventional power supply filtering and layout
techniques will further minimize signal degradation from the power supply.
It is recommended to use a 1 μF 0402 ceramic capacitor on each VDD for optimal performance. It is also suggested to include an
optional, single 0603 (resistor/ferrite) bead in series with each supply to enable additional filtering if needed.
Si5391 Reference Manual • Power Management
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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Rev. 0.5 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • January 11, 2022
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