General
Review Section 1.1.4.1 and verify the following for the custom schematic design:
- Review of the user's
guide
- Use of bulk and high
frequency capacitors.
- Number of capacitors used,
package and value.
- Voltage rating of the
capacitors used.
Schematic Review
Follow the below list for the custom
schematic design:
- All processor power rails use bulk and high frequency decoupling capacitors. The
critical power domains that require the focused attentions are the low voltage,
high current domains (VDD_CORE, VDDR_CORE).
- As a starting point, the recommendation is to follow the validated SK, or PDN
application note. When there is difference between the SK and PDN, the
recommendation is to follow the PDN. When information is not available in the
PDN, follow the SK implementation.
- The recommendation is to use Low-ESL capacitors connected with short traces to
minimize the PCB trace loop inductance.
- The recommendation is to verify each of the power rail pins has a decoupling
capacitor and each of the supply rail group has a bulk capacitor.
- Voltage rating of the capacitors used (> twice the worst-case applied voltage is
a commonly used guideline).
Additional
- In case difference is observed between the SK and
the PDN application note on the capacitor number recommendation and value, the
recommendation is to consider the recommendations in the PDN application
note
- While optimizing the capacitors, the recommendation is to perform static and dynamic PDN analysis to verify that the Reff, Cap LL, and Impedance targets are met
- In some situations, the SK uses 3-terminal capacitors, due to low inductance packaging. Make sure the 3-terminal capacitors connections are not implemented as an in-line or filter component
- The recommendation is to show the connections of the capacitor near to the relevant pin for ease of placement and routing