I am designing a 12 V → 5 V, 10 A buck power supply using only ceramic output capacitance and the TPS53353 family (or an equivalent DC-DC with ripple-injection). Key requirements and design choices:
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Vin: 12 V
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Vout: 5 V
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Iout (max): 10 A
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Soft-start: 2.8 ms
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Mode: Forced conduction / FCCM
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Switching frequency: 400 kHz
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Inductor: 2.2 µH, 8.6 mohm, 20% tolerance
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R_trip (RT resistor): 75 kohm
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Output capacitors: five × 100 µF ceramic capacitors (parallel), no polymer or electrolytic capacitors
When I use the Excel tool (which uses the polymer-capacitor stability formulae copied from the design section of the datasheet), the calculated ESR_Min (for stability) is greater than ESR_Max and the sheet flags a red warning. The spreadsheet’s stability criterion and the ESR bounds appear to be based on polymer capacitor ESR models.
My question: Can I safely ignore this warning because I am using only ceramic capacitors (very low ESR) and I am implementing the ripple-injection topology recommended in the datasheet.
I have attached the Excel sheet used for the calculations. 10A 12V-5V.xlsx