
MPC8572E PowerQUICC III Integrated Processor Hardware Specifications, Rev. 5
Freescale Semiconductor
79
High-Speed Serial Interfaces (HSSI)
clock driver chip manufacturer to verify whether this connection scheme is compatible with a particular
clock driver chip.
Figure 50. AC-Coupled Differential Connection with LVPECL Clock Driver (Reference Only)
Figure 51 shows the SerDes reference clock connection reference circuits for a single-ended clock driver.
It assumes the DC levels of the clock driver are compatible with MPC8572E SerDes reference clock
input’s DC requirement.
Figure 51. Single-Ended Connection (Reference Only)
15.2.4
AC Requirements for SerDes Reference Clocks
The clock driver selected should provide a high quality reference clock with low phase noise and
cycle-to-cycle jitter. Phase noise less than 100KHz can be tracked by the PLL and data recovery loops and
is less of a problem. Phase noise above 15MHz is filtered by the PLL. The most problematic phase noise
50
Ω
50
Ω
SD
n_REF_CLK
SD
n_REF_CLK
Clock Driver
100
Ω differential PWB trace
SerDes Refer.
CLK Receiver
Clock Driver
CLK_Out
LVPECL CLK
Driver Chip
R2
R1
MPC8572E
R1
10nF
50
Ω
50
Ω
SD
n_REF_CLK
SD
n_REF_CLK
100
Ω differential PWB trace
SerDes Refer.
CLK Receiver
Clock Driver
CLK_Out
Single-Ended
CLK Driver Chip
MPC8572E
33
Ω
Total 50
Ω. Assume clock driver’s
output impedance is about 16
Ω.
50
Ω