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In this 8th issue, we will introduce "Malfunction Examples and Solutions" based on five typical examples. diverse failures can occur when designing the power supply part of FPGAs. It can be caused by layout, peripheral components, sequence, patterns, etc.
We hope that the following examples of faulty operation and their solutions will be helpful for your future FPGA power supply design.
Case 1: Output failure caused by layout
Symptom: Output voltage waveform goes back and forth between specific voltages like a triangular wave.
Cause: VIA was touching the pad in the pattern placement prohibited area on the backside.
Remedy: Stable output by relocating the VIA and not drawing patterns in the prohibited area.
Note: Check the package section in the datasheet and do not place patterns or VIA in the prohibited area. Check the package section in the datasheet and do not place patterns or VIAs in the prohibited area.
Case 2: Operation failure caused by layout
Symptom: The device moves but generates excessive heat.
Cause: The AVIN extraction pattern that branches from VIN is close to the PVIN current loop and generates noise.
Remedy: By pulling the pattern from the root of VIN (Kelvin connection), noise contamination was alleviated and heat generation was stopped.
Note: Refer to pattern examples and design guide. Note: Refer to the pattern examples and design guide to create a pattern that minimizes noise contamination to the power supply and feedback.
Case 3: Influence by peripheral components
Symptom: No output at power-on
Cause: Over-current detection due to excessive output capacitance
Remedy: Normal start-up by setting appropriate output capacitance
Note: There is a maximum value for output capacitance / Check the maximum capacitance value in the datasheet of each device.
Case 4: Sequence-related defect
Symptom: Output voltage starts to rise but falls off in the middle and the power supply does not start up.
Cause: The startup sequence was not followed and an overcurrent was detected because more current than the limit was flowing at startup.
Remedy: By following the startup sequence, unnecessary current was eliminated and the device started up safely.
Note: Cyclone, Note: Cyclone, Arria, some Stratix IV and V series and later have a startup sequence / Refer to the Power-Up Sequence section in the Power Management section of the device handbook to ensure proper startup of each power supply line.
We hope that the above examples of failures and their solutions will be helpful to you when designing FPGA power supplies in the future.
If you would like to know more about the failure cases, please see the power supply column (summary of failure cases and notes).
In the next column, we will introduce using PDN tool provided by Intel.
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