While trying to implement an IoT solution using a quad-band mobile network module, supporting GSM,UMTS,LTE (2/3/4G), I advised to add all the following capacitor values to the modules power bus.
I have read several EE-SE answers on the subject and now understand that they are used for decoupling and evening out both LF and HF noise variations on the power bus.
Some relevant posts include:
- What's the purpose of two capacitors in parallel?
- Decoupling capacitors: what size and how many?
- Multiple identical parallel capacitors
- How to know exact Decoupling Capacitor values for supply voltages?
- how can i calculate decoupling capacitor value?
- How to choose capacitor for an IC
- Calculating the value of bypass capacitors for an amplifier
- Is there a formula to determine the size of decoupling capacitors?
To summarize briefly:
- Large Capacitors handles low frequency noise and output load changes.
- Small capacitors handle noise and fast transients.
- Parallel capacitors results in a lower Equivalent Series Resistance (ESR) than a single capacitor of larger value.
- LF capacitors (with higher ESR) have good performance in a wider range of frequency.
- Using multiple capacitors would not only reduce reduce the heat generated (by ESR), but would also help spread the heat.
- A decoupling capacitor is not only chosen by its Capacitance, but also by its ESR (Equivalent Series Resistance) and its ESL (Equivalent Series Inductance).
Q: (a) How are these values determined?
Q: (b) Why does small capacitors handle transient noise better than larger ones?