How to operate MC13213 with Li-ion rechargeable battery?

[lekkal]

Hi all,

    I have designed MC13213 board which has to operate with rechargeable Li-ion battery(3.7V), it also includes charge management (controller) IC. But as per the datasheet of mc1321x the operating voltage is 3.0V(max 3.4V). What kind of circuit should be used to get 3.0V from Li-ion battery(3.7V). Can I give 3.7V to MC1321x through a diode? Thanks in advance.




Regards,
Lekkal

[JimDon]

Use a voltage regulator.

This is an example.

You can get this part for at little as .50 qty 1.
There are many others to choose from, TI has them as well.
You need to figure out current draw as well.

[peg]

Hello,

The regulator quoted will not work as the dropout voltage is too high.
You need to check some things here.
What terminal voltage do you have while charging? May exceed max volts while charging with simple diode!
What does the terminal voltage over the whole discharge curve look like? If it is at all steep and you have some kind of dropout voltage for the regulator you may be throwing away a significant proportion of the battery life.

[bigmac]

Hello Lekkal,

You might wish to consider using a regulated, charge pump device.  I recall that some of these encompass the output voltage within their allowable input voltage range.  Their output regulation is mediocre, but may be adequate for your task.  However, you will also need to consider their quiescent current on battery life.

Regards,

Mac

[JimDon]

Actually shes right, you do want a better drop out voltage than that.
You also need to consider how low you will allow the battery to go.
If you pull li-ion battery too low you will kill them sooner.

You need to take a long hard look at the battery in question, and the recommended discard level.
Since this chip is good down to 2V, and 2.4V is the minimum discharge for li-ion cells (yours could be higher), you need to figure this out. Also need to know current draw.

For example this one 
Which has a max of .2v drop out (it's CMOS rather than bipolar) - if you got  the 2V one, it would be perfect (if 200ma is enough juice) as you are not supposed take the battery below that. Leaves some margin.

If  you go with charge pumps, you may have noise considerations, but you can longer battery life.