mpc8378e Freescale Semiconductor, Inc, mpc8378e Datasheet - Page 87

• Manufacturer Part Number: mpc8378e
• Description: Powerquicc Ii Pro Processor Hardware Specifications
• Manufacturer: Freescale Semiconductor, Inc

that the LVPECL clock driver’s output impedance is 50 Ω. R1 is used to DC-bias the LVPECL outputs
prior to AC-coupling. Its value could be ranged from 140 Ω to 240 Ω depending on clock driver vendor’s
requirement. R2 is used together with the SerDes reference clock receiver’s 50 Ω termination resistor to
attenuate the LVPECL output’s differential peak level such that it meets the device SerDes reference
clock’s differential input amplitude requirement (between 200 mV and 800 mV differential peak). For
example, if the LVPECL output’s differential peak is 900 mV and the desired SerDes reference clock input
amplitude is selected as 600 mV, the attenuation factor is 0.67, which requires R2 = 25 Ω. Please consult
clock driver chip manufacturer to verify whether this connection scheme is compatible with a particular
clock driver chip.
Freescale Semiconductor
LVPECL CLK Driver Chip
Clock Driver
Clock Driver
Figure 61. AC-Coupled Differential Connection with LVPECL Clock Driver (Reference Only)
CLK_Out
CLK_Out
MPC8378E PowerQUICC II Pro Processor Hardware Specifications, Rev. 3
R1
R1
100 Ω differential PWB trace
R2
R2
10 nF
10 nF
SD n _REF_CLK
SD n _REF_CLK
50 Ω
High-Speed Serial Interfaces (HSSI)
50 Ω
MPC8378E
SerDes Refer.
CLK Receiver
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