I'm attempting to use a Dallas Semi DS1307 RTC (real time clock) with a supercap power backup.

Seems the cap isn't charging from the pin as I expected it would, that some other means of keeping the charge must be supplied.

Does anyone know of an app note for doing this? Thanks.
Posted on 2004-03-14 12:27:14 by Ernie
Ahh... you use a DS1340 instead, which has that circuitry built in.

(I *thought* I saw it there)
Posted on 2004-03-27 00:28:32 by Ernie
The DS1307 does not have this feature. I am assuming you mean the DS1306.

On the DS1306 the trickle charger is disabled on power-up and it must be enabled by writing 1010 to bits 7:4 of the Trickle Charge Register (0x91). Also, you must select either 1 or two diodes (bits 3:2) and the value of the series resistor (bits 1:0). Note that if these bits are not set properly, the trickle charger will not be enabled.

See page 8 of the latest datasheet.
Posted on 2004-03-30 11:18:05 by VVV
No, I meant the DS1340. See previous post.
Posted on 2004-04-01 14:21:07 by Ernie