Hello - we are designing a 15W, 12Vout, DCM flyback using the UCC28730 controller.
The Vs pin is specified at -0.75V to 7V.
I am wondering about the -0.75V spec. Typically the aux voltage feeding Vs will be significantly less than -0.75V.
On some of the TI reference designs (e.g., TIDM512A), a Shockley diode and a Zener diode are used to clamp the Vs voltage but, unless i am missing something, this doesnt limit the negative voltage to -0.75V. Also, the datasheet implies that the aux voltage is sampled while the mosfet is on. I am pretty sure the aux voltage is negative during that sample time.
Can you please provide guidance on the spec? And also on how the input (run) and input (stop) values are determined?
Thanks!
Brett