Hello,
We use the nPM2100 EK for getting familiar with nPM2100 for its potential use in our project where we aim to use single AAA battery for powering it.
Our usage profile is simulated in the measurement attached below, where:
- top chart represents output voltage ~3.3V and input voltage (AAA battery)
- middle chart represents current drawn from the battery
- bottom chart represents an approximated AAA battery internal resistance (rough estimate - it shouldn't be compared to standard DS values)
Long story short, the battery is periodically loaded with ~50mA @ VOUT (~3.3V) - 1minute ON, 1 minute OFF. During the ON state, in the middle, the load is increased (for 5s) to ~100mA @ VOUT (~3.3V) which is the maximum we expect to draw from the battery.
We test when the output voltage drops below the desired 3.3V level which happens at the end of the measurement. At this state, the output voltage drops and the battery current increases.
Question:
Could you advise why the measured battery current saturates ~600mA when we have the IBALIM set to 800mA?
IMHO:
- In case the bottleneck was the battery, its voltage would drop further, right? It doesn't do that.
- The inductor selected inside the EK seems to have good saturation current rating.
We also used the default config of 600mA, the measured values were lower ~540mA.
Our measurement is performed with INA228 with 0.1Ohm shunt resistor, ~1 sample/second. It's quite under sampled. On the other hand, since IBATLIM is "Battery (valley) current limit setting", I believe the 800mA we set is actually the threshold when the ON state is re-activated again (the inductor gets charged again). So the average value would be higher than this level BUT it's lower...
Thank you!