• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 47 subscribers
  • Views 339 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.

OPA838: PCB layout for OPA838

Behnam Madadnia
Intellectual 420 points
Part Number: OPA838

Dear all, 

In the datasheet of the OPA838 there are the following recommendations for PCB layout:

1.Signal routing must be direct and as short as possible into and out of the op amp.

2. The feedback path must be short and direct avoiding vias if possible.

3. Ground or power planes must be removed from directly under the negative input and output pins of the amplifier.

But something is not clear for me, regarding the feedback trace:  

It is mentioned that : Place feedback resistor on the bottom of PCB between pins 4 and 6:

Should I necessarily put the feedback resistor on the bottom layer? do I need to remove ground plane underneath the feedback trace as well? 

This is my current layout in a 8 layer PCB, so everything is on top layer, the feedback resistor and the capacitor in the feedback loop:

Schematic :

Layout:

Would you please share a reference PCB circuit deign file (Altium) or a general guide line for OPA layout that I can follow? The I can design  a PCB with all the necessary considerations. Besides, I need some recommendation to improve my PCB layout.

Best regards,

Behnam,

  • +1
    TI__Genius 11390 points

    Hi Behnam,

    That is an interesting note that was added. I would suggest referencing the OPA838EVM we have available when working on your specific layout. The EVM is your best bet in terms of following the best PCB design practices. The EVM's product page can be found here and the user's guide can be found here. I also attached the Gerber files specific to that EVM design as another point of reference. As for the question about removing planes along the feedback path, we definitely recommend at the bare minimum to remove layers under the -IN/Out pin along with the pad connected with that pin, however some prefer to remove the layers under those pins along with the entire feedback path. The OPA838EVM design removes the layers along the feedback path.

    HSP024A_Gerbers.zip

    Best regards,

    Ignacio