LM2674: LM2674 transient response

Hello Sandeep,

Are you stepping the load from 15mA to 250mA. If yes how you are doing it. 

How you are measuring your VOUT? Are you using differential probes?

Do you see the same issue while ramping load slowly?

Are you using the custom EVM or TI EVM?

Best Regards,

Ankit Gupta

Hi,

I am using LCD backlight on/OFF(0 to 220mA)+LED (ON) as load. And I had tried with external electronic load also.

Vout i am measuring with normal DSO Probe across the Cout. Soldered two short connecting points across capacitor and connected the probe without the ground looping wire.

I am using custome board for the testing

Hello Sandeep,

Can you please measure your VOUT with the differential probe and check if it is not measurement artifact coming into your probe. If the issue persists, please share the waveform of Vout, SW, Inductor current, and load.

Best Regards,
Ankit Gupta

LM2674 Waveforms at different loads.pdf

Hello Sandeep,

Thanks for sharing the waveforms.

In the attached pdf I don't see any waveforms of high voltage dip. can you please recreate the issue and append the waveforms in the file you sent out. And please add the Inductor current waveform as well in your scope-shots. Thanks!

Best Regards,

Ankit Gupta

Application Engineer

Dear Ankit,

Condition 3 in the pdf is mentioned the transient behavior of IC when it is switching from 10mA to 270mA. Switching node and input wave form is also captured.

Second wave form of the condition 3 is the zoomed waveform of the first one.

The transient is almost 150mV.

Thanks and reghards

Sandeep 

Hello Sandeep,

Thanks for the clarification.

To improve transient response, can you please use the output cap with smaller ESR may be in the range of 50mohms.

Best Regards,

Ankit Gupta

Application Engineer