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DS90UB947-Q1: Ferrite bead selection and unused pin termination

Peter Bain
Prodigy 60 points
Part Number: DS90UB947-Q1

Hi guys,

I have a couple queries about this device I am hoping you can help with.

  1. I found this thread on choosing power rail ferrite beads:
    e2e.ti.com/.../832770
    My confusion is that the data sheet lists max IDD11 at 469mA and max IDD18 at 75mA, significantly less than those mentioned in the above thread. Given it is a checkerboard pattern test I doubled those currents when selecting ferrite beads.
    I had initially chosen these:
    VDD18: BLM18HE152SN1D which is 1.5kohm 500mA
    VDD11: BLM18PG121SH1D which is 120ohm 2A. There are 3 in total. One for VDDL11, one for VDDO(A/P)11, and one for VDD(A/HS/DP/DS)11
    Can you please confirm the correct current ratings? I am assume the datasheet is more reliable.
  2. ISO 26262 - functional safety standard for the automotive industry
    Are you able to confirm whether this device meets this standard or whether you will be obtaining certification for it?

Thanks, Peter

  • 0
    TI__Mastermind 30515 points

    Hi Peter,

    For the FB rating design, generally it is accepted with 40% deratiing. so you can use the 2A FB for VDDL11 and 500mA FB for VDD18.

    regarding the function safety, this is on system-level function safety design, including error/fault detection and system's response to reduce and remove its impact. For UB947 device, we provide the phy layer error detection (such as CRC error, lock indication etc.) to improve your system safety design level.

    best regards,

    Steven