12. Power Management
12.1 Power Management Features
Several unused functions can be powered down to minimize power consumption. The registers listed in in the following table are used
for powering down different features.
Table 12.1. Power Management Registers
Register Name
Hex Address [Bit Field]
Function
Si5341
Si5340
PDN
0x001E[0]
This bit allows powering down the device. The serial
interface remains powered during power down mode.
OUT0_PDN
OUT1_PDN
OUT2_PDN
OUT3_PDN
OUT4_PDN
OUT5_PDN
OUT6_PDN
OUT7_PDN
OUT8_PDN
OUT9_PDN
0x0108[0]
0x010D[0]
0x0112[0]
0x0117[0]
0x011C[0]
0x0121[0]
0x0126[0]
0x012B[0]
0x0130[0]
0x013A[0]
0x0112[0]
0x011C[0]
0x0126[0]
0x012B[0]
—
—
—
—
—
—
Powers down unused clock outputs.
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
12.2 Power Supply Recommendations
The power supply filtering generally is important for optimal timing performance. The Si5341/0 devices have multiple stages of on-chip
regulation to minimize the impact of board level noise on clock jitter.
It is recommended to use a 0402, 1.0 μF ceramic capacitor on each VDD for optimal performance. Because of the extensive internal
voltage regulation this will be sufficient unless the power supply has very high noise. If the power supply might have very high noise,
then it is suggested to include an optional, single 0603 (resistor/ferrite) bead in series with each supply to enable additional filtering.
This resistor/ferrite should initially be a 0 Ω resistor. If additional supply filtering is needed then a ferrite component can replace the 0 Ω
resistor.
12.3 Grounding Vias
The pad on the bottom of the device functions as both the sole electrical ground and primary heat transfer path. Hence it is important to
minimize the inductance and maximize the heat transfer from this pad to the internal ground plane of the pcb. Use no less than 25 vias
from the center pad to a ground plane under the device. In general more vias will perform better. Having the ground plane near the top
layer will also help to minimize the via inductance from the device to ground and maximize the heat transfer away from the device.
Si5341, Si5340 Rev D Family 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. 1.3 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 26, 2021
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