Output Overvoltage protection with COMP pin?

[cupoftea]

Hi,
Is it OK to pull down the COMP pin of LTC3723 with a NPN when in overvoltaged output?
As in the attached LTspice and jpeg

LTC3723

https://www.analog.com/media/en/technical-documentation/data-sheets/372312f.pdf

 

[Taihung]

Hi
I am not sure about your question.
In spec, LTC/ADI mention their example circuit is OK - Opto is NPN with base is actived by energy of light.
Your circuit will not work properly. Because your comparator not use smithtrigger or latching type or like compensation (analog output).
The ouput maybe rise of and shutdown -> ringing.

 

[cupoftea]

Thanks, the comparator and NPN is only for overvoltage handling, not regulation. I agree it needs Hysteresis though, thanks.
Basically the question i am asking is....is it OK to hard-short the COMP pin to GND?

 

[KlausST]

Hi,

My question is:why?
On overvoltage the output of the error amplifier (COMP) will be LOW anyways.

I don't see the benefit.

Klaus

 

[stenzer]

Hi,

have you had a closer look at the function description of the UVLO pin (see below). For me it sound like that one can be used instead of the COMP pin to fulfill your overvoltage protection. You migth have a look if this fits with your chosen soft-start cycle.

Input to Program System Turn-On and Turn-Off Voltages. The nominal threshold of the UVLO comparator is 5.0V. UVLO is connected to the main DC system feed through a resistor divider. When the UVLO threshold is exceeded, the TC3723-1/LTC3723-2 commences a soft-start cycle and a 10μA (nominal) current is fed out of UVLO to program the esired amount of system hysteresis. The hysteresis level can be adjusted by changing the resistance of the divider. UVLO can also be used to terminate all switching by pulling UVLO down to less than 4V. An open drain or collector switch can perform this function without changing the system turn on or turn off voltages.​

BR