Re: Using batteries with RTC Dallas ds1306

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I am using RTC Dallas ds1306 operated on 3.3V. I have connected a 3V

lithium

backup battery to the Vbat pin. > > I have a problem that the actual voltage of all the cr2032 3V lithium that

found is 3.2-3.3. The problem is that the ds1306 stays all the time in the > write protected mode because VCC1 is not greater than VBAT +0.2V. > > Any ideas where can I find batteries with lower voltage or a way to lower > the backup voltage on Vbat pin (I tried to put a diode but it didn?t work > because the current is too low).

You could try to create a negative voltage of 0.6V, and connect the minus of the battery to that, subtracting 0.6V when the system is running: diode clocksignal -----||----.----KA-------.------.---------.---- -0.6V to minus battery 10nF | | | | | | K diode | 100K 10nF A 1M | | | | | | | | gnd -----------'-------------'------'---------'---- GND

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Don't know if it works.

I vagely recall another method of generating a few 100mv negative, with just one transistor in a rather strange configuration. Just can't remember how ;)