• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 32 subscribers
  • Views 875 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DS125BR401A Capacitor Selection

Hong Tay
Expert 2465 points
Other Parts Discussed in Thread: DS125BR401AEVM, DS125BR401A

Hi all,

Any idea with the capacitor selection for DS125BR401A? In datasheet there is 0.1uF recommended. In PCIe usually a 0.1uF is used and for SATA a 0.01uF is used. For DS125BR401AEVM, 0.22uF is used instead. 

Any idea what is the capacitor value between 0.1uF and 0.22uF effect? Your comment is appreciated.

Thanks.

  • 0
    TI__Mastermind 29635 points
    Hi Hong,

    For PCIe, the recommended cap value of 0.22 uF is determined by the PCIe specification. The choice of AC coupling capacitor is such that it complies with the PCIe standard (Section 4.3.3.12.3), which calls for 75-265 nF for Gen 1/2 and 176-265 nF for Gen 3. The value of 0.22uF satisfies both these requirements. However, if you only need PCIe Gen 1-2, you could use a 0.1 uF if desired.

    For SAS/SATA, the max A.C. coupling capacitor specified in SAS-3 SCSI-3 standard is 12 nF (~0.01 uF is fine).

    The choice of capacitor depends on the specification you are using, due to differences in data patterns and encoding used.

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Expert 2465 points

    Hi Michael,

    Thanks for your help. It is useful for us.