Each of the four different inputs IN0-IN3 can be configured as single-ended dc-coupled standard CMOS, non-standard CMOS or
pulsed CMOS inputs. In all cases, the inputs should be terminated near the device input pins. In these configurations CMOS mode is
enabled via register setting "IN_PULSED_CMOS_EN" = 1 for each input. Note from the data sheet that the Standard CMOS selection
has higher VIL and VIH settings than the non-standard/ pulsed CMOS Input buffer selection. See the data sheet for the max VIL
and min VIH values for both Standard CMOS vs Non-standard CMOS & Pulsed CMOS selection. In general, following the “Standard
AC-Coupled Single-Ended” arrangement shown above will give superior jitter performance than the dc-coupled arrangements below.
Non-Standard or Pulsed CMOS
3.3 V, 2.5 V, 1.8 V LVCMOS
INx
50
*
R2
*R1
RS
RS matches the CMOS driver to a 50
ohm transmission line (if used)
INxb
Standard CMOS
INx
3.3 V, 2.5 V, 1.8 V
LVCMOS
Standard CMOS
*R1
*R2
50
RS
RS matches the CMOS driver to a 50
ohm transmission line (if used)
INxb
Clock IC
Non-Standard
Or
Pulsed CMOS
Clock IC
* Attenuation circuit not required for 1.8 V input or if all input specifications in data sheet are met.
* Attenuation circuit recommended but not required if input specifications in data sheet are met.
Figure 3.2. Input Terminations for DC-Coupled Standard CMOS and Non-Standard/Pulsed CMOS Inputs
Standard CMOS refers to a signal with a swing of (1.8 V, 2.5 V or 3.3 V) +/- 5% that complies with the specified maximum VIL and
minimum VIH specifications in the data sheet. Refer to the data sheet for the VIL and VIH specifications. For non-compliant inputs,
a resistive attenuator is required as shown. It is not recommended to add the attenuation circuit for compliant inputs as it adversely
affects the signal integrity at the input pins. Note that maximum input frequency cannot be guaranteed with the attenuator circuit. If an
input exceeds 3.3 V +5% then the input must be attenuated before going into the chip.
Si5386 Rev. E Reference Manual • Clock Inputs
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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