Low Power Regulators

[andybarrett1]

Charlie

Totally missed you asking (My Bad).

Application is 818, 1307RTC and 1620LCD. No Analogs. One vibration sensor DI as interrupt.

Wakes up on vibration. Displays time for 20Seconds Goes back to sleep.... Time stamp is recorded on remote DVD System by a camera.

At moment all running from a pp3 9volt .. LDO reg and 5volts. Looking to drop to 3.3v and use a better source of power.

Hope that explains enough ??

Thanks all for reading.

[Ioannis]

You said there is room for two AA batteries if I understood right. With just one battery and the following suggestion you will have more working time on 3.3 volts draining an AA alkaline really flat.

http://www.picbasic.co.uk/forum/show...836#post131836

Ioannis

[Charlie]

Both the RTC and LCD are 5V devices - RTC min is 4.5V, LCD min is 4.7 V.
So you really can't run your circuit at 3.3 V.
You will either need to use Ioannis' suggestion (which I also recommend), or go back to your 2936 regulator with at least a 6V battery. The 9V batteries have pretty low capacity - you might be better off with a couple 3V button cells; I have not worked out the details on those.

[AvionicsMaster1]

I'm just curious and was wondering:

MAX1620/MAX1621 states it can use a range of voltage between 3 to 5.5 volts.
DS1390 states it can do 2.97 to 5.5 volts.
16LF818 states it can do up to 2 to 5.5 volts.

So with maybe a little parts massaging you could use a 3.7 battery. Though pricey and needing a connection could you use two of these or something similar to get the life you desire? http://www.newark.com/dantona-indust...mah/dp/14N3902 They are thinner than a 9 volt battery so two could fit where one 9 volt battery currently resides.

[andybarrett1]

Both the RTC and LCD are 5V devices - RTC min is 4.5V, LCD min is 4.7 V.
So you really can't run your circuit at 3.3 V.
You will either need to use Ioannis' suggestion (which I also recommend), or go back to your 2936 regulator with at least a 6V battery. The 9V batteries have pretty low capacity - you might be better off with a couple 3V button cells; I have not worked out the details on those.

Hi yes the present circuit is built around a 5v supply....BUT :-

Looking to upgrade using LF818/19, LCD 3.3v and different RTC ...1307 has lousy timekeeping :-(

Application remains same... just maybe different parts!

BR
Andy

[Charlie]

Hi yes the present circuit is built around a 5v supply....BUT :-

Looking to upgrade using LF818/19, LCD 3.3v and different RTC ...1307 has lousy timekeeping :-(

Application remains same... just maybe different parts!

BR
Andy

You'll need to choose those parts to know your supply tolerance. The answers are all in the data sheets.