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 datasheet that the Standard CMOS selection
has higher VIL and VIH settings than the non-standard/ pulsed CMOS Input buffer selection. Please see the datasheet 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
3.3V, 2.5V, 1.8V LVCMOS
INx
50
*R2
*R1
RS
RS matches the CMOS driver to a 50
ohm transmission line (if used)
INxb
Standard CMOS
INx
3.3V, 2.5V, 1.8V 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 1.8V input or if all input specifications in datasheet are met.
* Attenuation circuit recommended but not required if input specifications in datasheet are met.
Figure 5.3. Input Terminations for DC Coupled Standard CMOS and Non-Standard/Pulsed CMOS Inputs
Standard CMOS refers to a signal with a swing of (1.8V, 2.5V or 3.3V) +/- 5% that complies with the specified maximum VIL and mini-
mum VIH specifications in the datasheet. Please refer to the datasheet 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 af-
fects the signal integrity at the input pins. Note that maximum input frequency cannot be guaranteed with the attenuator circuit. If an
input exceeds 3.3V +5% then the input must be attenuated before going into the chip.
Si5397/96 Reference Manual
Clock Inputs
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