The Pin is 10V/100mA.How to support 300mA GPRS module?

Hi All,

Currently I am designing a power management system for GPRS modem.

The input power is 10V/100mA. The VBATT programmed from DC-DC Buck Regulator (LM3845) is set to 4V. DC-DC Buck Regulator has current limit protection function. So i programmed it to 100mA also.


Pout = Pin x efficiency.
Assume efficiency = 90%.

4V x IBATT = 10V x 100mA x 90%
So the expected IBATT should be 225mA.


However, GPRS current drawn average is around 300mA in Class 8.
Therefore, the extra current should be supported by Lithium Battery and supercapacitor.

Any one has the idea of how to choose super capacitor or the lithium Battery?
How about the hardware connection for Battery? Parallel or Series from DC-DC Buck Regulator? I am using IWOW TR-900 GPRS module.

Thank you.

Regards,
Elfrec

You should look more carefully at your "use model", specifically
what the maximum short-term TX duty cycle is. That may give
you a low enough "average" current that you can use the filter
bank to ride out the TX burst.

elfrec said:

However, GPRS current drawn average is around 300mA in Class 8. Therefore, the extra current should be supported by Lithium Battery and supercapacitor.

Click to expand...

Your peak current is going to be much greater than this - could easily be 2A or more depending on the module, and the band.