I'm using the LTC3805 flyback in a configuration with feedback through an opto similar to the "typical application" on page 17 of the datasheet:
However, I run the system at very light loads sometimes and I am wondering what the Ith clamping thresholds are as well as the maximum clamping currents. I need to know how low I need to be able to pull Ith over temperature and with part-to-part variations to ensure that the system shuts off when I'm pulling light loads. in the simulation pulling it below 0.7V ensures it shuts off, but this is only a nominal value.
Additionally, the D4 diode I'm using has higher leakaged currents at high temperatures, I need to know what kind of currents the Ith pin can safely clamp continuously over temperature, since at higher temperatures that reverse-bias saturation current can get high, I may need to re-think my diode. However I need both pieces of information in order to make this decision.
If, for example, the maximum voltage that you can set Ith to at which the gate drive still shuts off is 0.6V over all temperature/process variation, and closer to 0.8V at cold, then the D4 voltage drop can be fairly high and still meet requirements and thus the reverse current doesn't have to be as high. If, for example, the Ith clamping current can be as high as 2mA or so continuously at hot, then the reverse current can be high and I am permitted to choose a diode with a smaller voltage drop.
Any help anyone could provide would be greatly appreciated.