TPS51396A: inductor synchronizes with internal mosfet

Hi,

This looks normal. What is your main application condition (Vin, Vo, Io)? Do you have a schematic? Because the inductor selection need to refer your application, I can help to double check it. Thanks.

Aurora

Thank you for your reply,  Please look below my main application condition.

Vin=12V , Vo=5V, I=5A

Hi,

There are some problem with you schematic:

1. The SS capacitor(C407) is too large. 1uF means the SS time is 120ms, which is too long. Pls remove it or change it smaller, like 18nF for 2.2ms soft start time.

2. The output capacitor seems not enough, our suggested Cout min is 66uF(3pcs*22uF). Because Cout will affect the loop stable, so pls refer to our datasheet and add more capacitor.

Thanks.

Aurora

Hi, 

I have done this and I saw differences. In the photo below you can see the current spike is lower, with 120uF decoupling capacitors.

So I would like to ask you if it ok to see that spike,

Thank you,

Hi,

You have also removed C407 right? For Cout, which type capacitor do you use? Electrolytic capacitors or ceramic capacitors (like MLCC)? Because our chip already has a compensation circuit inside, please use ceramic capacitors with smaller ESR. Thanks.

Aurora

Yes, I have removed the C407, and all capacitors are ceramic MLCC.  

Hi,

Can you also test the IL and SW waveform under full load condition? I mean 12V to 5V/5A. Thanks.

Aurora