REG102: REG102NA-3.3/3K

Hi Ali,

This is an older device so I will make some recommendations that are hopefully helpful to you.  But first, to your questions:

1. The REG102 does not require an output capacitor.
2. The NR pin is used to filter the internal reference voltage.  In LDO's, the dominant noise source is the reference voltage which if left alone is gained up by the internal high gain amplifier.  So designers place a large series resistor internal to the LDO between this reference and the error amp input, and the user places a shunt capacitor on the NR pin to GND.  This forms an RC filter on the reference voltage prior to the error amplifier and helps reduce noise.  This is optional and is not required, but can be helpful for those applications where ultra low noise is a premium spec.

Due to its age, the REG102 is not the cheapest or smallest solution.  If you need 200mA you should look at the TPS7A03, which comes in a 1mm X 1mm package.  The TPS7A03 requires a 1uF capacitor however this solution will likely still be smaller and cheaper, and you may already have this cap on board anyway in the form of decoupling for your other electronics. The REG102 is priced at over $1 each (1,000 piece pricing) while the TPS7A03 is priced at $0.268 (1,000 piece pricing).  The 1uF capacitor - if you need it - should not cost very much, so this solution will save you some money.

The smallest package of the REG102 is roughly 3mm x 3mm.  This is much larger than the TPS7A03, at just 1mm x 1mm, and it will still take more space when you add the 1uF Cout (if you do not already have that in your design).

The quiescent current of the REG102 is 600uA at max load and 10nA at shutoff.  The quiescent current of the TPS7A03 is just 200nA at max load and 3nA at shutoff.  So your battery life will be much longer with the TPS7A03.

If you need even less quiescent current at max load, the TPS7A02 is an option.  It is a drop in replacement for the TPS7A03 but the TPS7A02 has just 25nA of quiescent current while at load (and 3nA at shutdown) - further extending your battery life.  The TPS7A02 is a little more expensive ($0.453 per 1,000 piece pricing) but it will still be cheaper than the REG102.  We are also working on releasing the TPS7A02 in incredibly small chip scale options: 0.667mm X 0.667 mm (see page 44 of the TPS7A02 datasheet).  Monitor TI.com for when those are available if this interests you.

I hope this helps.

Thanks,

Stephen