I'm currently trying to design a system that incorporates an ADP5092 which can use a supercapacitor as the storage element but I am also considering other similar PMIC chips so this is more for reference. In this application the load system will include a transmitter so there will occasionally be large short duration current draws at a maximum of around 130-140 mA for sub-millisecond durations.
In the ADP5092 datasheet there are reference designs which mention a specific 220mF supercap is rated at 5V and has low ESR (300 mΩ) and is fairly expensive.
My understanding is that the PMIC voltage into the storage element should be well regulated and for example if configured for 3.3V should output reliably at 3.3V to the storage element. Does this mean that a supercap voltage rating could be chosen for 3.3V + negative tolerance?
e.g. tolerance -20%, 80% --> minimum 1.2 * 3.3 = 3.96V+ ratingIs the ESR value important:
- In general for a power storage supercapacitor?
- For this application (intermittent high TX current draws)?
If the ESR is not important a larger variety of supercaps are available with prices up to 5x lower than the one used in the example could be used and lower voltage rating further increases the available options due to the generally low voltage of supercaps.
