These tiny DC-DC boost converters (step-up) generate 5V output voltage from a very small input voltage of >0.9V. The extremely low start-up voltage makes it possible to use a single AA or AAA battery (for example) to power a 5V device, or microcontroller project.
The output current depends on the input voltage, and a very low input voltage of just about 1V for example only delivers an output current of <100mA at 5V. With 2 batteries (3V) the max. output current reaches already about 250-300mA, and 400-600mA is possible with a single-cell 3.7V lithium battery depending on its charging status.
– The efficiency is max. 96%, depending on input voltage and output current.
– The max. output current is 600mA, depending on the input voltage.
Please do your math and understand the relation between supply current, supply voltage, and output current:
For example, an output current of 450mA means an output power of 2.25W. If you have an input voltage of 3.7V, the input current is about (2.25W / 3.7V / 90% =) 680mA.