I am trying to make a simple Press ON - Hold OFF latching circuits using a momentary swicth. Here is a very well explained method. I made the exact same as fig6, with same passive value, but using differents MOSFET : Si2312CDS and Si2333CDS. Also not I am using a Schotkky diode MBR0530 instead of the BAV99. My main power is a regulated 3.3V. I fixed the Auto-OFF configuration, as I would like the system to stay switch OFF at boot.
The left part is the 3.3V regulation from a sigle cell LiPo battery. On the right end the POWER_OFF signal is controled by a microcontroller GPIO in order to switch OFF by software.
After soldering a prototype, some functions looks to be OK :
- Press ON : it is powering ON when short press is applyed to switch
- Hold OFF : need to hold the switch for several second to switch OFF the system
But I also have an unwanted behaviour :
- when OFF, it automatically switch ON after 2 seconds or so...
This does not look like the Auto-OFF(/ON) feature, even if at first boot the system goes ON (after 2 seconds) but we are in Auto-OFF case... It is more because it does not keep the OFF state...
Maybe because I use the Si2312/33 MOSFETs, that have Vgs different that the recommended iRF7319, and the passive components values are triggering the switch ON procedure ???
Does anybody can help me looking for the issue ? I can stick my oscilloscope into the system, but I am not sure to know what I should see...