TOP270EG - Not able to start

Posted by: Saravanan_S on 07/03/2025

HI Team,

I am currently using TOP270EG IC for my current new design SMPS.

I am facing startup issue. Unable get IC power on.

Note : I am not used PI design given transformer spec , Instead of I used another one flyback (65Khz to )transformer which is used our previous design(Used Transformer spec attached)

1-My question is for testing purpose the can i use any other flyback transformer or PI recommended transformer is necessary ?

2- Without transformer , how to i check the IC ?

Thanks

Saravanan s

Files

Screenshot 2025-07-04 104154.png (66.37 KB)

Comments

Hello Saravanan,

To answer your questions,

It is recommended to use the transformer generated by PI Expert/XLS. Most of the time, the design will not work properly if you use a premade transformer that was not designed for your requirements.
Without powering up the circuit, you can check if the IC is damaged by checking if any of the pins that should not be shorted are shorted

1- Yeah , Understood.

2- Ques 2 Related to TOPSwitch-JX General Test Circuit. I tested the circuit as given in data sheet Figure-35 ( above one also I am get any output )

The test circuit is just to test certain functionality of the IC.

You will not get any proper output from your design with the test circuit and without the transformer.

" The test circuit is just to test certain functionality of the IC. "

Yeah, Understood. i am also try to test ( Figure 35 ) functionality of IC for my understanding. Unfortunately that one also not get any output.

Could you pls explain what type of output will come?

Hello Saravanan,

Some of the functions that the test circuit can check are:

The F pin functionality, where the device will switch at 132kHz when connected to source and 66kHz when connected to the source pin.
The UV/OV thresholds by adjusting the components attached to the V pin.
The remote ON/OFF function of the X pin by using S3.

It cannot test the output characteristic or current limit measurements though, as stated in the note below the figure.