TPS51220A: Power output are abnormal

Hi Vincent,

Could you post the abnormal waveforms? Please probe the SW, Vout node of the abnormal channel. Thanks!

Regards,

Hao 

Hi, Hao,

As attached, CH2 is EN1(PIN_4), CH1 is 5V output.

BR,

Vincent. 

Hi Vincent,

It's (SW) switching node, not EN. And, could you set the time scale to show the detail switching waveform? Just like the waveform below,

BTW, could you figure out why there is a "glitch" on the enable?

Regards,

Hao

Hi, Hao,

Sorry, I don't have current probe, see attached, CH2 is SW (PIN_32) when power on...

BR,

Vincent.

Hi Vincent,

1. I've checked the schematic. Looks like the inductor ripple is a little bit large here. I would suggest to use 1.5uH for 3.3V, and 2.2uH for 5V.

2. Could you help to make it sure that, both channels are able to work independently as long as the other is disabled? Could you post the normal operation waveform as the example I gave(Add some loading, like 5A, and set the time scale to 2us)? 

I'd like to check if the switching is normal. If it's working normally, the SW waveform should be like the example I posted. 

3. Suppose 2 channels can work normally when only one of them is enabled. This kind of issue is probably related to PCB layout. There might be some interference or noise coupling between the two channels, especially on the sensitive FB, CSP/CSN signal tracks on PCB. Please post the layout here, or send to me by email, sam.zhang@ti.com.

Thanks!

Regards,

Hao