I have question about Diagnostic output DIAG1 of L6375S. I measured its behavior when I have open load condition and high VIN+ (when the undervoltage is away). I was changing power supply of integrated circuit from zero to supply voltage , where the undervoltage is out , output mosfet is switch on, and there is output voltage on output (pin2). Voltage for VIN+ input ( pin 7) was realized by divider from supply voltage.
I supposed from datasheet that DIAG1 (pin 5) is low all the time. Diag 1 is low until undervoltage is present and when is not under voltage starts state high input (VIN+) and open load, this is low too, by datasheet, but I have measured this waveform.
ChA - Vsupply, ChB - Diag1 (pin 5) voltage, ChC - IN+ voltage , ChD - Output voltage
I understand that supply voltage started to be higher than undervoltage and output power mosfet switch on when Vsupply is 7,5V. But I do not understand why DIAG1 goes high. VIN+ is 4,32V this should be high over every treshold ranges and hysteresis. And I have open output, nothing is connects (with transil), and any current flows. And in this case for 70us Diag1 signalize wrong because I have output power, I want output to be switched on, but nothing is connect on output and current does not flow and DIAG1 have to be low by truth table in datasheet to signalize required state is not achieved.
I would like to know if it is somethong wrong in my settings or it is feature of L6375S. And if it is the feature, I would like to know if it is the same time for every L6375S (when I will have IN+ in high when undervoltage is out) or it could be longer if I will have another IC L6375S or some another setting. And if it can be different I would like to know the longest time it could be because of filter this.
And I have little additional question. I do not know how I have to understand the levels on IN+ pin in datasheet. I do not understand what means pin high level voltage from 2 to Vs-3 or 15V, depends on Vs. It means that high level voltage could be even 15V in some case or high level voltage at VIN+ shouldn´t be higher than 15V (which is lower than absolute maximum ratings) for comfort operating area for IC.
Does anybody know why this is like that and what it exactly means?
