i am using AD9912 as a LO source for battery operated equipment. for that one i am desining power supply section( input volatge from battery is 14.8Volt )
1) 14.8 V to 5V through Switching regulator (part No RECOM regulator) then LDO AD3338 for 3.3 Volt
2) 14.8V to 2.2 V through Switching regulator(part no yet not finalized, LMZ1002 from TI) then LDO ADP172 for 1.8 Volt (300mA Load)
how much PSRR and ripple will be achieved with ADP172 (because drop out volatge is less than 1 Volt)
or we can decrase the input to ADP172 to increase the efficiency insipte PSRR & Ripple will not reduced .
two switching regulator in one board will not create any problem ( because board contain RF circuits.) or i have go to any other approch.