• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 99 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.

THVD1424: THVD1424 externa pull-up/down requirement

Nir Hasidim
Prodigy 30 points
Part Number: THVD1424


In our design, the control lines are: RE, DE, SLR are controled by MCU (1.8V VIO) for maximum flexibilty and minimizing the current consumption. We also have a very tight size constrains. We don't want to add pull-up/down resistors if it is not required.

from the datasheet (layout guidelines): "Use 1-kOhm to 10-kOhm pull-up and pull-down resistors for logic lines to limit noise currents in these lines during transient events ".

Can you please detail what will be the consequences in case we don't add external pull-up/down resistors?

Regards

 

 

 

  • 0
    TI__Guru* 77791 points

    Nir,

    Nir Hasidim said:
    Can you please detail what will be the consequences in case we don't add external pull-up/down resistors?

    These devices have internal pulls up/downs at around 2M ohms (maybe 30% tolerance). 

    So if there is noise on the pin/net, the 2M ohm resistors provide a weak bias. If the noise is strong enough, it could temporarily flip the input signal's digital logic. 

    If your application runs off of battery power, doesn't have switching sources, and isn't sitting next to a power station or motor then you likely won't see much noise that could cause this to flip. Conversely, if your board has a motor or some source of high inductive high current draw source or sits next to a high power switching element, then you could end up with noise in your system that could affect the device's inputs because the biasing may not hold the input above/below their ViH/ViL thresholds.

    -Bobby