• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 33 subscribers
  • Views 532 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

DP83822H: Bias Resistor tolerance

user576134
Prodigy 110 points
Part Number: DP83822H

The datasheet of the DP83822H says "A 4.87 kΩ +/-1% resistor must be connected from RBIAS to GND."

In your "DP83822 EVM Getting Started" you use a thik film resistor (CRCW04024K87FKED) wich has a tolerance of 1% but a stability of deltaR/R = 1 % for 1000 h at 70 ° C and 100ppm temperatur tolerance. So the overall tolerance is much more than 1%.

I want to know wich overall tolerance for the bias resistor is needed. 1% can not be the answer.

  • 0
    TI__Mastermind 23675 points
    Hi,

    1% is suggested to be within IEEE PMA compliance. The DP83822H is a current mode line driver and uses the RBIAS for its current mirror.
    If you use a resistor with variance, the drive strength can change and you could get higher or lower voltage swing depending on how the resistance changes.

    In the EVM, I do agree that the resistor is not the best since it has variability over temperature. When conducting PMA IEEE compliance, it is generally done at room temperature, which is why this resistor was chosen. You will not see a performance difference though.