TPS55340: Wrong output voltage and inductor makes sound

Roberto del Pozo Gallardo

Intellectual 440 points

Part Number: TPS55340

Dear Sir/Madam,

I used the WEBENCH® POWER DESIGNER to design a DC/DC converter with the following parameters:

Vin min = 2.7V
Vin max = 4.5V
Vout = 12V
Iout = 1A

With no load and a small load like 1kohm the circuit is working good.

But when I connect a load for example 15ohm the circuit don't give the good output (10V instead of 12) and the inductor or something else is making sound.

The strange thing is that when I use no load and turn the converter on and after that connect a load of 15 ohm the converter is working fine.

What can I do to solve this problem?

I would like to thank you in advance and I am looking forward to your reply.

Regards,

Roberto

over 4 years ago

0 Jasper Li over 4 years ago

TI__Mastermind 46905 points

Hi Roberto,

TPS55340 is not a good solution for such application. why do you select this device?

the device may triggers current limit or become unstable. could you measure the Vbat and 12V_BAT waveform when observe the problem.

0 Roberto del Pozo Gallardo over 4 years ago in reply to Jasper Li

Intellectual 440 points

Dear Jasper Li,

I choose it because it was the cheapest option and the first option listed by WEBENCH® POWER DESIGNER.

Voltage before Diode

Output voltage (blue input voltage)

I hope you can help with this.

Regards,

Roberto

0 Jasper Li over 4 years ago in reply to Roberto del Pozo Gallardo

TI__Mastermind 46905 points

Hi Roberto,

in the first waveform, the time scale is only 200ns? if yes, the switching frequency is 2MHz, not 800KHz as setting.

do you observe similar behavior in several boards? make sure the issue is not caused by assembling.

0 Roberto del Pozo Gallardo over 4 years ago in reply to Jasper Li

Intellectual 440 points

Dear Jasper Li,

I see what I did wrong.

I used a 60R4 resistor instead of a 60K4 resistor.

I will try this tomorrow and let you know if that was the problem.

Thank you!

0 Jasper Li over 4 years ago in reply to Roberto del Pozo Gallardo

TI__Mastermind 46905 points

Hi Roberto,

I closed the post as I think you have solved the issue. if not, just reply below

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TPS55340: Wrong output voltage and inductor makes sound