Need to invert voltage detector behavior
Need to invert voltage detector behavior
(OP)
Greetings,
I have a voltage detector IC (Seiko) that outputs an active low (N-ch) as a result of a low voltage state (<5VDC). I also have a voltage regulator (LM2931) that can be turned ON via active low. The problem is that we would like the active low (which represents a low-battery or power fault condition) to DISABLE the regulator. As it is, the active low during the low battery condition would turn ON the regulator.
Any clever ideas on how to wire this to make it work? I have been looking for some sort of inverted voltage detector IC (active N-ch low when voltage is greater than detection voltage) to no avail. Power consumption needs to be kept very low, as this is a battery disconnect circuit of sorts.
Any suggestions would be much appreciated!
I have a voltage detector IC (Seiko) that outputs an active low (N-ch) as a result of a low voltage state (<5VDC). I also have a voltage regulator (LM2931) that can be turned ON via active low. The problem is that we would like the active low (which represents a low-battery or power fault condition) to DISABLE the regulator. As it is, the active low during the low battery condition would turn ON the regulator.
Any clever ideas on how to wire this to make it work? I have been looking for some sort of inverted voltage detector IC (active N-ch low when voltage is greater than detection voltage) to no avail. Power consumption needs to be kept very low, as this is a battery disconnect circuit of sorts.
Any suggestions would be much appreciated!





RE: Need to invert voltage detector behavior
RE: Need to invert voltage detector behavior
RE: Need to invert voltage detector behavior
Baring that you can use a P-FET or an N-FET to reverse a logic signal. However the problems this can cause are pretty numerous as the failing power can cause 'buzzing' of your control, or galloping, etc.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Need to invert voltage detector behavior
I think I will use a small n-fet to invert the logic at the shutdown pin. Thanks for the suggestion. I am a bit new to electrical design - could you explain to me about the potential 'galloping' problem? I'm looking forward to absorbing some new information.
RE: Need to invert voltage detector behavior
For instance a really common problem is;
The battery voltage drops.
The disable triggers.
The regulator is shut down.
The load evaporates.
The unloaded battery voltage rebounds.
The system turns ON.
The load returns.
The battery voltage drops....................
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Need to invert voltage detector behavior
Check these parts. They go to 70V in some cases and I'm sure some will auto shutdown.
h
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Need to invert voltage detector behavior
And I wish I knew about that part earlier - it looks very nice. Live and learn! The n-fet appears to be working well but hopefully I can simplify the design in the next round.
Thanks for the help.