8.4.2 Differential Output Swing Modes
There are two selectable differential output swing modes: Normal and High (also called low power mode). Each output can support a
unique mode.
Differential Normal Swing Mode—This is the usual selection for differential outputs and should be used, unless there is a specific
reason to do otherwise. When an output driver is configured in normal swing mode, its output swing is selectable as one of 7 settings
ranging from 200 mVpp_se to 800 mVpp_se in increments of 100 mV. Differential Output Voltage Swing Control Registers lists the
registers that control the output voltage swing. The output impedance in the Normal Swing Mode is 100 Ω differential. Any of the
terminations shown in
Figure 8.2 Supported Differential Output Terminations on page 29
are supported in this mode.
Differential High Swing Mode—When an output driver is configured in high swing mode, its output swing is configurable as one of 7
settings ranging from 400 mVpp_se to 1600 mVpp_se in increments of 200 mV. The output driver is in high impedance mode and
supports standard 50 Ω PCB traces. Any of the terminations shown in
Figure 8.2 Supported Differential Output Terminations on page 29
are supported. The use of High Swing mode will result in larger pk-pk output swings that draw less power. The trade off will be slower
rise and fall times.
Vpp_diff is 2 x Vpp_se as shown below.
OUTx
OUTx
Vpp_se
Vpp_se
Vpp_diff = 2*Vpp_se
Vcm
Vcm
Vcm
Figure 8.3. Vpp_se and Vpp_diff
Table 8.4. Differential Output Voltage Swing Control Registers
Setting Name
Hex Address [Bit Field]
Function
Si5391/Si5391P
OUT0A_AMPL
0105[6:4]
Sets the voltage swing (amplitude) for the differential output drivers when in
Normal differential format and Low Power differential format (
tings for LVDS, LVPECL, and HCSL on page 34
OUT0_AMPL
010A[6:4]
OUT1_AMPL
010F[6:4]
OUT2_AMPL
0114[6:4]
OUT3_AMPL
0119[6:4]
OUT4_AMPL
011E[6:4]
OUT5_AMPL
0123[6:4]
OUT6_AMPL
0128[6:4]
OUT7_AMPL
012D[6:4]
OUT8_AMPL
0132[6:4]
OUT9_AMPL
0137[6:4]
OUT9A_AMPL
013C[6:4]
Si5391 Reference Manual • Outputs
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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