Single Input Dual Output Voltage Regulator

[ciaranq]

Hey,

so my situation is this: Im currently trying to improve the efficiency of a wireless temperature sensor. On the board currently is a voltage regulator that drops the voltage from 7.4V to 3.3V essentially wasting a lot of the batterys power. My plan was to change the configuration of the batteries from series to parallel as to drop the voltage to 3.7V and double the capacity.
The issue with that is that i need a minimum of 4V to power the temperature sensor itself and 3.3V to power the XBee transmitter.
Having had a look online i have found a little device called a Buck-Boost converter which sounds ideal for what i require, a steady output voltage regardless of whether the input is higher or lower. But i can't find a device that allows me to input my 3.7V battery and output BOTH 3.3V and 4V+.

If anyone has better searching skills or knowledge in this area that would be fantastic.

Regards,
Ciarán

 

[KlausST]

Hi,

if you expect good results of a searchnig you need to have good informations first.

Like: current consumtion in idle / active, idle time, active time, battery type (chemistry, charge..), min and max battery voltage, expected battery lifetime and so on...

***
And maybe you could improve your design: 4V for a temperature sensor is quite unusual, there are plenty that work with 3V3....

Klaus

 

[Audioguru]

A Lithium battery cell averages 3.7V during a discharge. It is 4.20V when fully charged and is about 3.2V when it is almost dead and should have its load disconnected. It can supply MASSIVE current so if you connect two in parallel and their amount of charge is a little different then you will have an explosion or fire as the higher voltage one tries to charge the lower voltage one with its MASSIVE current.

 

[ads-ee]

I don't understand why the OP is changing the configuration of the batteries to parallel (bad idea). Leave them in series but use a switching supply module and their loss will drop dramatically compared to a linear regulator (assumed given the issue with power loss described). Something like this LM2717 would work, checked on Digikey and they are only ~$3.