DS1307

andys · Joined: 23 Oct 2006 Posts: 175

I have a DS1307 pcb module and i have little confusion about the power supply which is needed.

Can i used it with 3.3V power supply? (I read somewhere that need 5V but the battery is 3.6V)

temtronic · Posted: Wed Jan 08, 2014 7:59 pm

According to the datasheet the Supply voltage is 5 volts(4.5...5.5).
So, NO, you cannot use with a 3v3 power supply.
Vbat( the backup..keep alive supply) is 3volts. You use a typical 'coin cell' battery for Vbat.

hth
jay

Ttelmah · Joined: 11 Mar 2010 Posts: 19535

3.6v is too high for the battery. The specification in the data sheet is 3.5v _max_.

You need to distinguish what things ''do'. The battery keeps just the clock part of the chip running, _not_ the logic interface to the outside world.

If a supply is present on the main rail, that is more than approximately 1.3*Vbat, the logic interface wakes up, and the clock runs from the main supply. If the supply drops below 1.284*Vbat, the logic interface goes 'off', and just the clock keeps running off the battery.

The specification for Vbat, is 2v min, 3.5v max.
The specification for Vcc is 4.5v min, 5.5v max.

If the battery is as high at 3.6v, there is no guarantee that the switch over to running off the main rail, will happen correctly.

So, as temtronic says, 'no' the chip can't run off 3.3v. It needs 4.5v min, and your battery needs to be a slightly lower voltage type.

Best Wishes

asmallri · Joined: 12 Aug 2004 Posts: 1635 Location: Perth, Australia