Hi docmur
SHIPPING WARNING: of late, the airfreight powers that be have gotten very concerned about lithium batteries (including primary coin cells!!) on planes. So your usual suppliers (Digikey, Element14, Mouser, Sparkfun etc.)
may not be able to ship them. So for short runs I suggest you look for coin cells you can buy at your local hardware store.
Whew.
This is actually a surprisingly complicated question.
There are five considerations:
- Will your circuitry work OK over the whole CR2032 voltage range of 3.2 - 2.5V? (Note that you'll get voltage dips if you draw current pulses which could upset come circuitry). Here's a data sheet.
- Over the desired life of the battery, how many mAhr will the quiescent current (Iq) of the regulator consume?
- Over the desired life of the battery, how many mAhr will controlling the output voltage of the regulator help you save?
- Can you afford the space?
- Would it be worth the money?
You should be aware that buck-boost converters are often a lot less efficient than a buck or a boost. You might do better to adjust your design to make it a buck-only or boost-only supply. The TPS62736 is perhaps a good candidate for a buck design (Iq < 0.5uA!)
When you evaluate the power savings in your main circuit, you need to look at active mode and sleep / standby mode consumption. If you're going for ultra-low power sleep modes (e.g. MSP430 something), moving from 3.3V to 2.5V could reduce the sleep current by quite some extent. If you spend lots of time in active mode, remember you need to convert the current drawn by your load into equivalent battery current to make the numbers work.
The spreadsheets are calling youuuuuuuu...
[Edit: swapped data sheet reference, upped maximum coin cell voltage from 3.0V to 3.2V]
Home
Help
Search
Login
Register
