how to Convert 3.7v to 3v

[Deexith Hasan]

my input is 3.7v lithium battery.I need output 3v <=500ma.

 

[malli_1729]

Check the LDO. There will be many options from different manufacturers. What is minimum voltage of Lithium battery @ input for which output should be regulated to 3V?

 

[crutschow]

How close does it need to be to 3V?

 

[bharathclinten]

minimum voltage of li battery is 3.3v

I need to replace 2 AA size battery so I need 3v output.

 

[djsfantasi]

minimum voltage of li battery is 3.3v

I need to replace 2 AA size battery so I need 3v output.

Put a silicon diode in series with the battery. It will drop 0.7 volts. How much current does the load draw? The diode you select depends on this.

 

[bharathclinten]

<= 200ma. Battery at full charge has 4.2v so after diode voltage drop i will get 3.5v ?
can I go for LDO like TLV701/2/3/4 or TPS793 ? or suggest me some popular widely available LDO's

 

[d123]

Hi,

Check dropout voltage graphs and PD in datasheets.

TPS73801 (I'm familiar with it) shows 100mV at 25ºC and 150mV at 125ºC for 200mA out, but that is with Vin = Vout, I guess that may work for you, the PD formula at the bottom of the datasheet is worth going through before buying the wrong part; also the TPS793 from looking at dropout voltage in the datasheet, ditto PD calculations. TLV701/2/3/4, perhaps not, as 701 and 704 are only 150mA.
Best suggestions for LDOs are suffering an hour or so comparing on manufacturer product pages using the filters to narrow the options, and reading a few datasheets. LT may have something with a cherry on the top you really prefer over something TI offer, or maybe ST or Intersil have something better/cheaper, or the same but more expensive, and so on. Really good to browse a few datasheets and make a personal informed choice, then check back if you have any doubts.

I like Micrel LDOs, but I wouldn't use them in everything, it would be a waste of money sometimes, I like the TI TPS73801 as it is idiot-proof/indestructible, but you may not.

All this said to help, as reading datasheets and comparing price/ku is very informative. TPS793 presumably fine.

 

[asdf44]

Yeah, you need a LDO with a DO that is actually L, like 0.3V which you should be able to find.

Though if you're actually replacing AA batteries the circuit in question shouldn't need a full 3V since AA batteries drop significantly over their life. Any load that actually runs on them should tolerate 2.5V or even lower.