14. RC Delay Capacitor Selection

When the board powers ON, the controller should not start immediately — it needs a short reset delay (~5 ms) to let the power supply stabilize. This is done with a simple RC timing circuit.

RC Time Constant Calculation:

τ = R × C = 100kΩ × 10nF = 1 ms

Total delay ≈ 5τ = 5 × 1 ms = 5 ms

For a timing circuit, the capacitor’s value must stay accurate and stable across temperature. This is why a C0G/NP0 dielectric is required — it has near-zero capacitance change with temperature, unlike X7R which can drift ±15% over its temperature range.

Required: 10nF · ±5% · C0G/NP0 · ≥25V · 0603 · SMD · −55°C to +125°C · RoHS

Go to DigiKey.com → Capacitors → Ceramic Capacitors

Apply these filters:

• Capacitance → 10000pF (10nF)
• Voltage Rated → 25V or higher
• Temperature Coefficient → C0G, NP0
• Tolerance → ±5% or tighter
• Package / Case → 0603 (1608 Metric)
• Part Status → Active

Tip: On DigiKey, C0G and NP0 are the same dielectric — just different naming conventions. Both will appear under the C0G/NP0 filter option.

Tip: Never use X7R or Y5V for timing circuits. X7R can drift ±15% with temperature, and Y5V can lose up to 80% capacitance — both would make the delay wildly inaccurate.

The filtered list will show many matching parts. Before you pick one, check: Is it Active? Is stock available? Is the manufacturer reputable? Is a datasheet available?

Full checklist: How to Select a Safe, Production-Ready Component — EWskills Guide

➡ View Matching Parts — 10nF, 0603, C0G/NP0, ±5%, ≥25V