Other Parts Discussed in Thread: LM5180EVM-S05
Tool/software:
Hi,
I have an issue in a new design using the LM5181. First some infomations:
Requirements:
Vin: 6-36V Default 12V
Vout: 6V
Iout: 0.5mA to 100mA
Selected transformer:
LPD8035V-223MRC
* 1:1
* Lmag: 22µH
* DCR: 34mohm
* Leak: 305nH
Primary circuits:
Rfb: 63.4kohm
Snupper:
* Shottky: PMEG1020EA
* Zener: DFLZ10-7 (10V)
Secondary circuit:
Shottky: PMEG1020EA
Cout: 2µ2F
Rload: 150ohm (No zener at this measurement)
Result:
Blue curve: Vout (7,5V when switching.)
Yellow curve: Vsw
The scenario repeats frequently. The input current is around 50mA. The output voltage moves up and down together with the input voltage. I.e. no voltage regulation.
I cannot ficure out why the LM5181 shuts down. Basically there should be two reasons, over temperature and over current. The LM5181 has no significant temperature raise. But I do not beleave that it is the current limitter. If I reduce the load to a 330 ohm resister, the output voltage is just raising. Redusing the Rfb to 50kohm, seems not to make any change to the output voltage.
Any advices? Thanks in advance.
