LM5009 Buck converter off time?

[treez]

Hello,
A buck converter that uses the LM5009 control chip has an internal FET, which has a current limit of 310mA. If the FET current limit is reached, an OFF time kicks in. The off time is determined by the resistor RCL as on page 9 of the datasheet.
However, if the FB pin voltage falls below 2.5V before the duration of that off time, does the FET get turned back on anyway?

In other words, is the off time curtailed of the FB pin voltage falls below 2.5V?

LM5009 DATASHEET:
https://www.ti.com/lit/ds/symlink/lm5009.pdf

 

[Dan Mills]

Geez man, just read the datasheet allready, there is a picture (Figure 8) that answers this question.

In particular note that one of the inputs to the and gate feeding the set input of the SR latch is a 'complete' signal from the current limit off timer.
Also, switching the fet back on would seem to defeat the whole point of current limit in the event of a short circuit at the output.

Regards, Dan.

 

[D.A.(Tony)Stewart]

Actually this smart current limiter is intended for temp. shorts and auto recovery. So it will restart after the timeout.

Sometimes this is called the hickup mode.

 

[treez]

sorry I don't see why this is supposedly so clear, I admit that if the FB signal is less than 2.5V and the fet current hits the limit, then this needs the current limit off timer to run its full duration, as there may be a shorted output....however, if the FB pin is 2.5V or more, then it is perfectly acceptable , surely, for the off time to be curtailed by the FB pin falling below 2.5V, and for the FET to be switched on again.....surely this is the way to get a less noisy, and more beneficial operation?

It is perfectly natural , in most other current mode controllers, for the fet current to hit the sense peak, and then the fet be turned off.....it would not be natural to have the fet turning off for an inordinately long time in such occasions.