lm2576 on/off when undervoltage

[pozzari]

i have a 12v battery and lm2576, and it have a shutdown pin from lm2576 to a npn transistor.
when the battery goes below 11 volts i put the shutdown pin to high and the lm2576 turn off.

The problem is... when the battery arrives at 11 volts the lm2576 turn off and in this same moment it turn on again because the battery returns to more then 11 volts, then the lm2576 goes on again... and off again...

It is a spike ??

How to turn off the lm2576 when battery goes discharge to 11 volts and turn on only when voltage goes more than 12 volts or is recharging?

Sorry my bad english

 

[ashokok]

The problem is... when the battery arrives at 11 volts the lm2576 turn off and in this same moment it turn on again because the battery returns to more then 11 volts, then the lm2576 goes on again... and off again...

It is a spike ??

How to turn off the lm2576 when battery goes discharge to 11 volts and turn on only when voltage goes more than 12 volts or is recharging?

it is not the spike.
the battery voltage will rise when the load Disconnected due to internal resistance of the battery .
by using Comparator with Hysteresis you can turn on and off as you required.



P.Ashok Kumar

 

[dick_freebird]

You need at least one of these:

a stiffer input supply, whose load-sag at startup when the
converter hits into it at full load, is less than the UVLO
hysteresis. But the attributes here may be a "given" that
you don't get to constrain to your liking

more UVLO hysteresis, to accommodate the amount of
input load-sag that you are presented with. Here, you
may only be looking at a "present case" and not "worst
case". You need to deal with some range, which may be
unpleasantly wide.

a more leisurely startup, that doesn't try to slew from
no current to full current into the output filter and load
so abruptly. Enforcing a lower output dV/dt or di/dt may
keep you out of motorboating startup mode. Do you have
a "soft start" pin that will let you hang on a capacitor
and lower the startup ramp rate?