Hi,
We are designing something very similar to the "PMP4737" reference design, in order to supply power to a GSM modem from a Lithium Ion rechargeable battery to a GSM module.
But, we are surprised to see that the input voltage listed for the PMP4737 reference design is just 2.5V-3.6V. Is there a reason behind limiting this range, despite the output voltage being 4.5V? Or, can I expect to supply the voltage from a rechargeable Li Ion battery directly (upto 4.2V) and the circuit would still be able to "withstand" this? Although I see no reason it shouldn't (the VIN of the Boost Converter is rated for >5V), please confirm if there is any such issue.
Right now, our approach was to use the bq24253, but the output voltage would dip along with the battery, which is why we plan to put a boost converter at it's output to provide a stable 4.5V (or near about) supply. In case you have any other recommendation for such a system (USB chargeable Li Ion battery + sustained load of about 300-500mA, and GSM tx/rx peaks of 1.6-18A), please feel free to do so. Avoiding BGA/DSBGA parts would be great!
