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.
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.
Ahh... you use a DS1340 instead, which has that circuitry built in.
(I *thought* I saw it there)
(I *thought* I saw it there)
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.
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.
No, I meant the DS1340. See previous post.