Battery circuit to produce ±3V and +5V

[CaptainSpock]

Hi everyone,

I'm currently doing my Fyp project, which to design a portable system to monitor ankle brachial index.
I already have a PPG and ECG circuit but they both requires different power voltage. The ppg circuit uses ±3V to power op amp ic MCP602 and ECG uses +5V to power instrumenttation amp INA321 and op amp OPA336.
Can anyone advise me how to obtain the different voltages from a battery supply.

CaptainSpock

 

[mrarslanahmed]

use single power source lm7805 and lm7803 with respective filters.....

u will get required voltages with a single source....

 

[bjuric]

For -3V you can use dedicated IC that generates negative voltage, or google for 555 circuit for negative voltage generator. 5V input will give you about -3.3V.

 

[alexxx]

use single power source lm7805 and lm7803 with respective filters.....

Never heard of a 7803 before. Could you please provide a datasheet?

 

[mrarslanahmed]

alexxx i am sorry for giving wrong answer ...

**broken link removed**


above link may help

 

[alexxx]

alexxx i am sorry for giving wrong answer ...

Nothing to worry about for my part. It is just that CaptainSpock is searching for a solution and we wouldn't want to get him confused. ;-)

Battery circuit to produce ±3V and +5V

What is the battery's nominal voltage?

 

[CaptainSpock]

For now I'm using 2 1.5 volts bat to obtain ±3V by charge pump max865. But I'm unsure how to get the +5v power

CaptanSpock

 

[alexxx]

But I'm unsure how to get the +5v power

16.5V dropout voltage for linear regulators like 7805 is not negligible quantity, you need very small output current to avoid overheat. Maybe you should look into DC-DC converters like 34063.
https://www.onsemi.com/pub_link/Collateral/MC34063A-D.PDF

Hope that helped.

 

[CaptainSpock]

Thank for all your replies,

I'm thinking of using 4, 1.5V battery to achieve the 6V for INA321
then stepdown the voltage to ±3V

Can anyone tell me whether this is viable?

CaptainSpock

 

[kumarji]

It is not a good idea to do so

 

[CaptainSpock]

So what do you recommend?

 

[bjuric]

If you have the room, how about 6 batteries? First two will give you +3V, and two on top of that with a diode to drop the voltage to about +5.3V. And another two in "reverse" to get -3V. It is a bit too much, but eliminates all the converters and boosters.