Information about UVLO comparator

[kaitlyn]

Hallo friends,

Please give me some reference circuits of UVLO.
i just know it should be a comparator using voltage divider to make the volatge whatever you want . and then we need to compare this value with reference.

But what's the supply voltage for the comparator? if i need the 24V, 2.5V UVLO
can they use one comparator with 2.5 supply voltage?

i just have no idea of how the UVLO look like, please give me some clue

Kaitlyn

 

[aryajur]

uvlo comperator

The comparator you make should be operational at very low voltages to ensure UVLO operation happens correctly under all process corners. Same is with the reference! You can maybe make a reference of a Vbe or a Vth of a transistor.
One other easier way is to use the Bandgap cell. If you ratio the supply and apply it to the point where the bandgap voltage is generated you can use the property that when the supply would be such that the ratio comes out to be the bandgap voltage then only the voltages on the PTAT and the IPTAT branch will be equal and so it will be like a comparator.

 

[ycj]

uvlo

UVLO is just a reference and a comparator that can work under very low voltage.
An issue should be concerned: if the supply voltage is too low for UVLO to work properly, the circuits that supposed to be shutdown won't be turned on occasionally.
You will meet the issue in designing the UVLO.

 

[crossbow_123]

what is uvlo

Hi!

You can reference this paper for your design.

thanks very much

 

[dhasmana]

cmos uvlo circuit

Hi,
You can use a comparator with external resistors for getting the desired trip point and also the desired hysterysis.Check the book of CMOS analog ckt design by Allen Holberg.There is example of comparator with external (not inbuilt) hysterysis.
You can realise both clockwise and anti clock wise hysterysis.
Regards,
Dhasmana.

 

[jasonma2005]

uvlo power supply

It is really important to check the circuit state when supply is too low to start up the reference.
It is perfectly to involve a reference good detection circuit. if not, power on reset can be used.