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AC Coupling Capacitor Value for DM8168 SATA Interface

Julie Lambert
Intellectual 315 points
Other Parts Discussed in Thread: TMS320DM8168

Hi,

According to Table 8-95. SATA AC Coupling Capacitors Requirements of the TMS320DM8168 datasheet (SPRS614A), the SATA AC coupling capacitor value should be 1nF MIN, 10nF TYP and 12nF MAX. Similarily, in Table 27 – General Specifications of the Serial ATA Revision 2.6 specification, the AC coupling capacitance shall be 12nF max.

However, the capacitance used on the NETRA EVM schematics (sheet 12) is 0.1uF.

Question: Should we use 0.1uF or 10nF coupling capacitors?

Thanks,
Julie

  • 0
    TI__Mastermind 25055 points

    Julie,

    For SATA the AC decoupling value is not as critical since it's really only there to stop DC from messing up the very sensitive receiver signal levels so that the receiver can listen only to the signal and not any inter-board DC voltage offset.

    10nF is the typical capacitor value in the datasheet, but we are actually making a change in the next revision of the datasheet that shows a max recommended value of 100nF, since in most cases 0.1uF will also work just fine.

    Regards,
    Marc