LM2596S-ADJEVM: inductor ripple current

Rahul Roy

Prodigy 10 points

Part Number: LM2596S-ADJEVM
Other Parts Discussed in Thread: LM2596, LM2595

I am using LM2596 Device.

Our application is:

Vin=5V,Vo=3.8V,Io=1.7A

We used 33uH inductor and we observed two types of inductor current waveform at Vin, why this type of behaviour of the device.

Also above 7.3V input voltage inductor current same behaviour like in input 5.6V waveform.

We used Resistor value is Rup=2.2k ohm,Rlower=1.1k at feedback pin and Cff=10nF.

Device power up by DC power source.

Pls refer attached file i.

over 1 year ago

0 Rahul Roy over 1 year ago

Prodigy 10 points

Rupper=2.2kohm,Rlower=1.1kOhm used on feedback pin,CFF=10nF, voltage input given by DC Power source.

0 Youhao Xi over 1 year ago in reply to Rahul Roy

TI__Guru* 76005 points

Hello Rahul,

Thank you for using our devices. The waveforms looks like the subharmonic oscillations indicating your inductance is too small. Could you raise the inductor to 47uH or even higher?

Thanks,

Youhao

0 Rahul Roy over 1 year ago in reply to Youhao Xi

Prodigy 10 points

Hi Youhao Xi,

I have changed inductor from 47 to 68uH and 82uH but not improvement.

This waveform is ok or not.

If not then what impact on my system with with subharmonics please guide me.

Regards,

Rahul

0 Youhao Xi over 1 year ago in reply to Rahul Roy

TI__Guru* 76005 points

Hi Rahul,

The waveform shows your inductor tends to saturate because the current rising slope is bending up, which will require a higher slope compensation. Could you put back the original EVM inductor, or select an inductor of similar Isat as the EVM's original inductor?

You may also consider LM2595 which requires a smaller inductor.

Thanks,

Youhao

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LM2596S-ADJEVM: inductor ripple current