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I am designing a circuit that uses the TI TPS561201 buck converter. Reading the data sheet, I am slightly confused with the notation of "Not Installed" next to some of the components.

Questions:

  • What is the purpose of including an uninstalled component?
  • In what scenario would I include the capacitors in my circuit?

With capacitor C4, for example, why would the component be drawn in the schematic but then labeled "Not Installed"? I have attached the schematic with the symbols highlighted.

TI buck converter schematic

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  • \$\begingroup\$ C4 may have caused instability at certain gain/voltage settings. This was most likely found during final testing and flagged RED. \$\endgroup\$ – Sparky256 Jun 6 '18 at 4:06
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    \$\begingroup\$ In general, "not installed" components are options that generate different versions of the board and/or were detected as problematic during debug and integration and eliminated. In the first case, they will appear installed in some variants of the board, and uninstalled in others. In the latter case, if the component produced a problem, it will be removed or corrected in a later layout of the board. \$\endgroup\$ – Claudio Avi Chami Jun 6 '18 at 4:12
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It means on their reference design/eval board it is not installed. That means if you think you need more capacitance, you can add one. Since TI parts are cheap a saving a few pennies is a big deal so they leave off the caps. The feed back loop cap (C8) is usually useful if you need to stabilize the feedback loop for any reason.

enter image description here

TIP: if you have a question, it is good to poke around all the documentation you can find for that part (use the product page and any app notes they have, evaluation board files are always good to check), sometimes there is only a hint of more documentation in the datasheet or website. I'm not saying your wrong for posting the question, I'm suggesting a tool for future use.

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  • \$\begingroup\$ Thanks for your answer- very clear. I have read the full data sheet a couple of times and it did not explain the "Not Installed" piece (hence the question). I attached the screenshot only for brevity. \$\endgroup\$ – falling cat Jun 6 '18 at 5:00

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