Suitable DC-DC Buck converter for coin cell battery with Storage capacitor

Hans Christian Glittenberg

Hi,

We are looking for a DC-DC buck converter which will be used with a coin cell (3.6V down to about 2 Volts). The output voltage will be about 2.1 V.

In order to increase battery life, the maximum current drain from the battery should be around 2 mA for short periods only (some seconds). Coin cell battery capacity is reduced if exposed to high pulse currents.

During these seconds, the output storage capacitor should store enough energy to supply up to 20 to 40 mA for a short duration, typically 10 to 30 ms or thereabout. This ensures that the "high" pulse currents is not drawn from the battery itself.

I have found TS3310 from another manufacturer which have this capability. However, it is a boost converter. So, does TI have any DCDC converter which is designed to meet the criterion mentioned?

Regards,

over 9 years ago

0 Jasper Li over 9 years ago

TI__Mastermind 46905 points

please have a look at the reference design "Energy Buffering for Long-Life Battery Applications". it may help to solve your problem

0 Chris Glaser over 9 years ago

TI__Guru**** 150950 points

This reference design sounds like exactly what you are looking for: http://www.ti.com/tool/PMP9753

0 Hans Christian Glittenberg over 9 years ago in reply to Chris Glaser

Expert 2235 points

Thank you guys! Smart approach using the incremental step. I tried to follow the links inside the pdf for more detailed calculations - however it just points to the same document! It would be nice to see what portion of the losses is due to the resistor - however, they state the efficiency is 91 % for the converter alone, and the graph shows a bit below 90 % for the combined losses. So its not that much it seems.

Regarding figure 1, there seems to be a typo there. It states that the battery energy decreases with lighter loads (in the text inside the figure).

Also, there must be an error with figure 14. It states that there is drawn energy from the battery after the capacitor charge-up process has finished.

Best Regards,

0 Florian Feckl over 9 years ago in reply to Hans Christian Glittenberg

TI__Expert 7110 points

The losses for the incremental are quite low due to the small voltage steps and the therefore small resistor.

The Thionylclorid chemistry is quite complex. In the referred case of figure 1, the self discharge is taking over and therefore the extractable capacity is less.

In figure 14, the graph shows the Energy that has been drawn until the point in time from the battery.

0 Hans Christian Glittenberg over 9 years ago in reply to Florian Feckl

Expert 2235 points

Hi Florian,

Thanks. I got it now. Should have understood this myself at the time of reading.

Regards,

Power management

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Suitable DC-DC Buck converter for coin cell battery with Storage capacitor