Can't we use coin cell battery(CR2032, 220mAh) for MC13213 boards???

[lekkal]

Hi All,

I have prepared mc1321x board without external power amplifier and LNA, it is working with two AA batteries and with DC adapter but not working with coin cell or button cell battery. whenever I connect to coin cell battery voltage is dropping from 3V to 1.8V. Can we use lithium battery for MC1321x boards, if it is possible please forward the details of alternate coin cell battery. I am making a keyfob module, for that I can't use AA battery(since bigger in size) can anyone suggest me what kind of battery I can use to minimize the module size.Find the attached file for additional information on battery details which I have used.

Thanks,

Lekkal

[LightElf]

As stated in the CR2032 datasheet, recommended discharge current is 0.2 mA.
MC13213 supply current in run mode (at 16 MHz) is 6.5 mA and up to about 50 mA
in RF active mode. So CR2032 can't be used.

[bigmac]

Hello,

I would interpret the "recommended discharge current" to represent the average continuous current level, to achieve, in this case, a battery life of about 1000 hours.  It is probably the current level used to rate the mAh capacity of the battery.  Current peaks of short duration may exceed this value, limited by the internal resistance of the battery, particularly near the end of life of the battery.

Assuming the instantaneous load is 50-60ma, and with a voltage reduction of 1.2 volts, this would indicate internal resistance of about 20 ohms.  This seem to suggest that the battery you have been using is exhausted.  Perhaps you might measure the reduction of voltage with a fresh battery and a known load to get some idea of the allowable peak current for the battery.  It will also depend on the minimum voltage your project can tolerate, and what battery life you require.

If the CR2032 coin cell does prove to be inadequate, you might consider a larger Lithium coin cell such as CR2450.  Another possibility might be to use two CR2032 cells connected in parallel.

Regards,

Mac

[baddad]

Another solution I have seen used when a higher short duration current is needed than the supply can provide is a large cap.

If the battery can supply more than the average current needed, than you can use the battery as a source to charge a large cap (over a longer time), then the cap can provide the larger current to the output when needed.  Make sure the cap is large enough for the longest duration of high current needed and that there is enough time between outputs to re-charge the cap.

BadDad