Duo to Covid 19 closure I did not use my light for long time and when finally want to use it the batteries were dead :(
I measured the off mode current and find out it is 3 mA.
I am using a moded 105c driver running my FW
Do you have idea what can be the reason for such high leakage current?
This is my circuit:
And my FW:
Link
THX
Maybe it stays active instead of going to sleep?
Ie, there’s a difference between “it should” and “it does”. 
What do you mean stays active? Active current consumption for Attiny13a is ~uA and not miliamps
Active current is 2-3 mA at 4 V depending on frequency of the internal oscillator (figure 19-3 and 19-4). If you want less you have to configure power reduction as described in the datasheet.
It could be that your mcu isn’t being put in to power saving mod in the firmware (sleep). It could also be possible you have a tiny short somewhere but since your showing just about the correct amount of draw for the running of the mcu, that be my guess as others have said.
You could flash the driver with some other well tested firmware and see if the problem still exist. That rule out the firmware if it still draws the 3ma.
I would try the simplest first. Process of elimination.
Seems like I have a loot of datasheet reading to do.
If the problem is with the fuse burning another FW will not solve it am I right?
Which fuse?
The fuse that you have to burn in order to set some basic parameters before burning the FW simmilar to OTP
There’s not much you can do to save power via setting fuses other than disabling the internal oscillator. Just power down as much as possible while it’s off and wake it up via a pin change interrupt when you press the button.
The fuses set during programming, think of them like the bios for a computer. Windows is the firmware and the bios is the fuses.
Fuses set the perimenters and features mostly for the clock of the mcu.
Usually the FW author gives you the correct fuse settings to program with since they are dependent on each other for the clock timmings.
For the ATtiny13 you can only select between an internal 128 kHz oscillator for the watchdog, internal 4.8 or 9.6 MHz main oscillator or external oscillator via the fuses. Everything else (clock related) can be set during runtime via the clock prescaler.
But in this case you want to enter power-down mode as described in section 7 “Power Management and Sleep Modes”.