TPS62135: TPS621351 Output current fluctuates

Hi,

Colin will reply to you later today.

Hi, 

Could you send the schematic to us for check?

Also the waveforms is needed.

Thanks

Colin

I tried asking for help in the Chinese forum, but no one restored it. The Chinese area asked me to come to the English forum. The following pictures are the waveforms of 11.56V(1.95A) and 11.14V(1.87A). Yellow is the current, and blue is the duty cycle of SW. It gives me the feeling that the duty cycle is not at full load.

I tried asking for help in the Chinese forum, but no one restored it. The Chinese area asked me to come to the English forum. The following pictures are the waveforms of 11.56V(1.95A) and 11.14V(1.87A). Yellow is the current, and blue is the duty cycle of SW. It gives me the feeling that the duty cycle is not at full load.

Hi Sir,

Actually it met Ton-min limit when it output such low Vout.

Ton=Vout/(Vin*fsw)>=Ton_min.

You can see datasheet has stated that the lowest Vout is 0.8V.

Thanks

Colin

But my output doesn't go below 0.8V so I don't think it's solved.

Hi Sir,

What is your Vout?  The internal V_ref is 0.8V of this device. How could you change it to 0.298V? Could you send me the schematic for check?

Thanks

Colin

I think, n, is your understanding wrong? TPS621351 can set VFB voltage, I set 0.3V.

Hi Sir,

I got your point but still have some confusion about your R1 and R2 set in your description,

Could you send the schematic of this device to me, that would be more straightforward.

Thanks

Colin

Also could you narrow the time scale of the waveforms?

I  suggest you can choose FPWM and test again.

Thanks

Colin