I'm trying o use a LiSoCl2 battery in a low power GSM application. When the system is in standby only the microcontroller(MSP430) is powered(3.3v) and the GSM(5v) and sensor(5v) is turned off. The whole system consumes 50uA. The burst current when sending data over GSM is up to 2A, but my battery provides a maximum 400mA of discharge current. Some applications use auxiliary capacitor, but most capacitors have high leakage current. The converter used for provide 5v is LMR61428, when the system is in standby mode it is turned off.
What is the best way to avoid leakage current of an auxiliary capacitor? Is there a way to enable the capacitor only moments before using GSM to prevent leakage current?