TPS62808: TPS62808YKAR

Hi Lisa,

The efficiency of the LDO is defined as:

(Vout * Load Current) / (Vin * (Load Current + Quiescent Current) )

The quiescent current of the TPS7A21 is 6.5 uA typical.  How much current do you need?  If you do not need more than 200 mA, you may wish to consider the TPS7A02 (25 nA quiescent current), the TPS7A03 (200 nA quiescent current) or the TPS7A05 (1 uA quiescent current).  In general, at light loads an LDO will be more efficient.  At heavy loads the switching converter will be more efficient. 

Notice I am going down to 1uA in this plot.  If you have a load under 100nA, keep in mind that the leakage from your input and output capacitors will play role in your efficiency as well.

Thanks,

Stephen

Hi Lisa,

Will you need an input filter for the switching converter? If so then that will drop some additional power and that will slightly lower the efficiency of the switching converter option.  How much it will lower it, will depend on the filter you insert into your design.

I would look at the TPS7A02/3/5 LDO options and compare that with the TPS62808 switching converter option.  If you need to operate closer to 150mA most of the time, then the switching converter may offer higher efficiency.  If you need to operate at light loads most of the time, then the LDO will offer higher efficiency.  If you need the smallest cost or the smallest solution size, the LDO will be your best option.

Thanks,

Stephen