Tag
capacitors
4 articles.
- How long will the battery last? Estimating it properly
Capacity over average current is the easy part. Here is what the cell's rated drain, its internal resistance and the cutoff voltage do to that answer.
- Why an LDO oscillates: the output capacitor's ESR tunnel
The ESR zero that keeps a PMOS LDO stable, the tunnel where too little and too much both oscillate, why ceramics broke old parts, and what C_NR and C_FF trade.
- Your 2.2 µF is 0.68 µF: DC bias and the capacitance you did not buy
Ceramics lose capacitance under DC voltage. Würth measured a 25 V X7R part losing 69 % of its value at its rated voltage, and the datasheet never mentions it.
- Where the buck ripple comes from, and why more capacitance didn't help
The textbook ΔV = I/(8Cf) is the special case where ESR is zero. Where most real designs sit, output ripple is I·ESR, independent of capacitance and frequency.