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[SOLVED] Regulating power from 7.4 lith-poly battery

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SeriousTyro

SeriousTyro

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I have a 7.4V lith polymer battery. What I simply want to do is do two voltage dividers to get 5V and 2.5V. These voltage will then supply my microcontroller and op amps.

However, I cannot simply do this.
What are things I should look into, should I look into voltage regulators?
Is doing a voltage divider to get my 5V and 2.5V bad?
 

hi
voltage divider is not good solution because output voltage depends on load current and is not precise at all,
use voltage regulators
simply you can use a 5v regulator such as 7805 and a 2.5v regulator such as ld1086-25 but you should connect the input of 2.5v regulator to 5v ,
or you can use switching regulator for 2.5v
 
Thanks. Probably typo, u mean 5v --> 2.5V?
 

I mean connect the input of 5v regulator directly to 7.4v battery,
but connect the input of 2.5v regulator to output of 5v regulator
because if you connect the input of 2.5v reg directly to 7.4v you will have about 5 volts drop on your 2.5v reg and this will cause high power consumption on regulator and makes it hot(in case of linear regulators),
 
hamidmoallemi said:
simply you can use a 5v regulator such as 7805
Click to expand...
It will not work!
A 7.4V Li-Po battery slowly drops to only 6.0V as it is used. But a 7805 needs a minimum input of 6.5V for a regulated 5.0V output.
Use a "low-dropout" 5V regulator instead that works perfectly when its input voltage drops to 5.5V.
 
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