4.5.4 Recommended Settings for Differential LVPECL, LVDS, HCSL, and CML
Each differential output has four primary settings for control:
1. Normal or Low-Power Format
2. Amplitude (sometimes called Swing)
3. Common Mode Voltage
4. Stop High or Stop Low (See
4.7.1 Output Driver State When Disabled
The Normal mode setting includes an internal 100 Ω resistor between the OUT and OUTb pins. In Low-Power mode, this resistor
is removed, resulting in a higher output impedance. The increased impedance creates larger amplitudes for the same power while
reducing edge rates, which may increase jitter or phase noise. In either mode, the differential receiver must be properly terminated to
the PCB trace impedance for good system signal integrity.
Amplitude controls are as described in the previous section and also in more detail in
13. Appendix—Custom Differential Amplitude
". Common mode voltage selection is also described in more detail in this appendix.
Table 4.7. Recommended Settings for Differential LVPECL, LVDS, HCSL, and CML
Standard
VDDO
Mode
OUTx_FORMAT
OUTx_CM
OUTx_AMPL
(V)
(Dec)
(Dec)
(Dec)
LVPECL
3.3
Normal
1
11
6
LVPECL
2.5
Normal
1
11
6
LVDS
3.3
Normal
1
3
3
LVDS
2.5
Normal
1
11
3
Sub-LVDS
1
1.8
Normal
1
13
3
HCSL
2
3.3
Low-Power
2
13
3
HCSL
2
2.5
Low-Power
2
10
3
HCSL
2
1.8
Low-Power
2
13
3
Note:
1. The Sub-LVDS common mode voltage is not compliant with LVDS standards. Therefore, AC coupling the driver to an LVDS
receiver is required in this case.
2. Creates HCSL compatible signals, see HCSL receiver biasing network in
Figure 4.2 Si5386 Supported Differential Output
.
The output differential driver can also produce a wide range of CML compatible output amplitudes. See
Differential Amplitude Controls
for additional information.
Si5386 Rev. E Reference Manual • Output Clocks
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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Rev. 1.2 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • December 9, 2021
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