Hi there
I'm DIYing a non-isolated buck converter based on UC3573, whose design is basically a modification of the design given out in the datasheet of that IC (http://www.ti.com.cn/cn/lit/ds/symlink/uc3573.pdf -only changed the inductor, capacitor and freewheel diode due to different design requirement, and another modification I'll talk about below)
However the design failed to work, after "debugging" for a very long time it turn out that the gate output is ALWAYS pulled up to VCC—— as it drives a PMOS whose source pin is connected to VCC, the MOSFET remains "shut", always—— and I'm sure that the Gate Output and the VCC are not shorted, which indicates that the 3573 DID BOOT. I have disconnect EAINV from the feedback network and grounded it, but the problem remained.
Checked every pin with multimeter(I have the IC "fanned out"), and everything seems to be OK.
The other modification is that, as the value current sense capacitor is too small, I simply shorted CS and VCC and I wonder if this triggers the current protection mechanism. But I can't see why in the datasheet, to my understanding, it is not until the voltage drop on Rcs becomes larger than 0.43V that mechanism triggers.
I wanted to simulate with TINA-TI myself but I can't find the TINA model of UC3573, if you have that model, please let me know. And there's a evaluation kid of UC3573(http://www.ti.com.cn/cn/lit/an/slua199/slua199.pdf), shorting R1 and R2 shall simulate my case well, so if someone have that kid, would you please do me a favor by doing that simluation? Thank you very much.
Thanks for reading. If you have any idea on this problem or this chip, plz DO leave your comment, thank you
