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TMS320C6678: Can I use a resistor other than 45.3 ohm in PTV15 pin of TMS320C6678

HJ Roh
Prodigy 20 points
Part Number: TMS320C6678

All of the documentation available recommends a 45.3 ohm resistor on the PTV15 pin.

I'm working on a design that already utilizes a 22 ohm resistor.

I had problem what not booting DDR3. but After replacing the 45.3 ohm with 22 ohm, all the boards DDR3 can work now.

so I had question to you..

question 1 : Can I use a resistor other than 45.3 ohm in PTV15 pin of TMS320C6678 ?

question 2 : Any idea how a 45 ohm resistor would alter the driver?

below eval module has a note showing, The reason why I used  other resistor.

* DDR3 Drive Strength - TMDXEVM6678L_EVM_A101-1_DSN, 13 page DSP_DDR3(DSPM-8301E, Rev. A101-1)

70 ohm: 6mA

60 ohm: 7mA

50 ohm: 8mA

45 ohm: 9mA

40 ohm: 10mA

36 ohm: 11mA

That's the only reference I can find to adjusting the value beyond the 45.3 ohms documented elsewhere.

  • +1
    TI__Guru 52002 points

    Hello,

    TI does not recommend using a value other than 45.3 on the PTV pin.

    Regards,

    Kyle

  • 0 in reply to kcastille
    Prodigy 20 points

    Hello 

    I have additional question.
    The 6678 EVM schematic(TMDXEVM6678L_EVM_A101-1_DSN, 13 page DSP_DDR3) has other options besides 45.3 ohms(for example 36ohm, 40ohm... )
    is it wrong ? or     Is it experimental data what not recommending ?
    Regards,
    Roh