MPC8535EBVTATH datasheet(96/126 Pages) FREESCALE

96 / 126 page

MPC8535E PowerQUICC™ III Integrated Processor Hardware Specifications, Rev. 2

High-Speed Serial Interfaces

Freescale Semiconductor

Figure 64 shows the SerDes reference clock connection reference circuits for LVPECL type clock driver. Since LVPECL

driver’s DC levels (both common mode voltages and output swing) are incompatible with MPC8535E SerDes reference clock

input’s DC requirement, AC-coupling has to be used. Figure 64 assumes that the LVPECL clock driver’s output impedance is

Ω. R1 is used to DC-bias the LVPECL outputs prior to AC-coupling. Its value could be ranged from 140Ω to 240Ω 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 MPC8535E SerDes reference clock’s differential

input amplitude requirement (between 200mV and 800mV differential peak). For example, if the LVPECL output’s differential

peak is 900mV and the desired SerDes reference clock input amplitude is selected as 600mV, 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.

Figure 64. AC-Coupled Differential Connection with LVPECL Clock Driver (Reference Only)

Figure 65 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 MPC8535E SerDes reference clock input’s DC requirement.

Figure 65. Single-Ended Connection (Reference Only)

SDn_REF_CLK

Clock Driver

100

Ω differential PWB trace

SerDes Refer.

CLK Receiver

Clock Driver

CLK_Out

LVPECL CLK

Driver Chip

MPC8535E

10nF

10 nF

SDn_REF_CLK

100

Ω differential PWB trace

SerDes Refer.

CLK Receiver

Clock Driver

CLK_Out

Single-Ended

CLK Driver Chip

Total 50

Ω. Assume clock driver’s

output impedance is about 16

Ω.

MPC8535EBVTATH Datasheet(PDF) 96 Page - Freescale Semiconductor, Inc

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