I'm designing a 3V3 PSU for 12/6V (lead) battery powered (outdoor) application. Supposed load is 70mA but I plan sleep mode (50uA) with periodic wake-up (ATMega1284P with 32kHz (RTC) crystal). It means I need high efficiency under very light load. Hence I believe I need switching PSU IC designed for such scenario (TI calls it light-load support), mainly very low quiescent current (<30uA or so).
As Xbee module is to be powered from PSU there is Digi recommendation "*If you are using a switching regulator for your power supply, switching frequencies above 500 kHz are preferred. Power supply ripple should be limited to a maximum 250 mV peak to peak.*".
I found Texas Instruments
TPS62125 ICs. The former supports only max.75mA , the latter supports 300mA which seems perfect. Both chips offer efficiency 80-90% @ 70mA, 44% @ 50uA. But the
TPS62125 is available on miniature WSON socket which not too nice for hand hot air soldering. Even TPS62120 is only 75mA it has more user friendly SOT package but output current is too near to required current. There are other
TPS62xxx ICs (160, 177, ...) but they are not so good at light loads.
Can anybody confirm the idea is correct or is another recommended way how to achieve good result (e.g. using big/supercapacitor and forcing PSU power down when MCU is sleeping, low/high temperature issue?, maybe less efficient because of cap self discharging?).
Optionally if somebody has another suitable chip please provide reference.