• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 101 subscribers
  • Views 393 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.

C6678 PTV15

Xiang Chao
Intellectual 360 points

I am wondering what to do with C6678 pin G22, PTV15. The hardware design book doesn't mention it at all.

Should I tie it to gnd with a resister? or leave it unconnected?

 

thanks

 

Xiang Chao

  • 0
    TI__Mastermind 42545 points

    A precision resistor placed between the PTV15 pin and ground is used to closely tune the output impedance of the DDR interface drivers to 50ohms.  Presently the recommended value for this 1% resistor is 45.3 ohms. 

  • 0 in reply to Bill Taboada
    Expert 1560 points

    Bill, I'm working on a design that already utilizes a 47 ohm resistor so it would be beneficial from a sourcing perspective to try to re-use parts.  The eval module has a note showing:

    DDR3 Drive Strength:

    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.  Any idea how a 47 ohm resistor would alter the 50 ohm impedance of the driver?