Hello,

Can someone sugest me a good 3.3V regulator (step-down)?
It will be used to power a OEM board with tolerance of -100mV and +200mV.

Thanks!

 

use digikey's filtering to find a suitable part (or try to)

if you run into problems finding one, come back and post again.

 

I can't found none until now. LM3940 seems nice but needs 5V at its input.

Another important requirements:
Input voltage: 3.7V (battery)
Output current: > 200mA

If it was trough-hole would be nice, but SMD is also ok.

Thanks for the hint, I will keep searching!

 

Hello,

Just take a look at the LM3668 buck-boost converter:
http://www.national.com/pf/LM/LM3668.html#Overview

Bertus

 

For linear regulators, search for "LDO" == Low Drop Off.

That is the term for a linear regulator that requires little overhead above the regulation voltage.

But my other suggestion is that there are many switch-mode regulators that are designed for this conversion, that will allow the device to run even when the batteries get pretty low. They will take in for example, 2.8 - 4.2V and put out 3.3V. Disadvantages: generally use a coil and a couple caps for external components, and some added EMI.

 

not to be nit picky,

but isnt LDO = low drop out?

 

Sure, I guess so.

 

Here are a couple from Digi-Key:

Link #1
Link #2

 

Hello,

@jbeng:
The parts you show in the links will NOT work.
The input voltage needed is to high.
The OP wants to run on a lithium battery of 3.7 Volts.

Bertus