TPS61175 Inductor: DCR concerns

Vincent Rigolet

Other Parts Discussed in Thread: TPS61175

Hi,

We'd like to use the TPS61175 to boost our input voltage (3 to 4.2V) to Vout=12V. We used the webench tool (file attached) to define the external parts.

The point is that we're not happy with the specified inductor (Bourns SRN8040-6R8Y) since we have height restraints in our product.

We found an inductor (Vishay Dale IHLP2020BZER6R8M01) with the same inductance and similar rated currents. The main difference seems to come from the DCR which is around 150mohm for the vishay and 33mohm for the Bourns.

What could be the effect of such a DCR difference? I precise that our application is very intermittent: the TPS61175 will run 2*100ms a day....

Thanks for your help,

6574.Webench tps61175.pdf

over 12 years ago

0 Chris Glaser over 12 years ago

TI__Guru**** 150770 points

You should be able to put your chosen inductor back into webench and see what changes. The main item to change would be the efficiency It will go down with higher DCR. Other impacts should be minor.

0 Vincent Rigolet over 12 years ago in reply to Chris Glaser

Prodigy 120 points

Taking into account our low usage of the step up converter, the efficiency is not the most critical parameter. Anyway, I will put back the new inductor in webench to confirm this,

Thanks for your help,

0 Vincent Rigolet over 12 years ago in reply to Vincent Rigolet

Prodigy 120 points

Hi again,

We did a PCB using the webench results (attached file), with the Vishay Dale IHLP2020BZER6R8M01 instead of the Bourns SRN8040-6R8Y.

The output voltage is ok (12.6V) @ no load, but it's decreasing when output current becames higher than 60mA. It's only 5.5V with a load that should draw 0.5A .

Do you have an idea of what is happening?

Regards,

3187.Webench tps61175 IHLP.pdf

0 Chris Glaser over 12 years ago in reply to Vincent Rigolet

TI__Guru**** 150770 points

Since this is no longer about how to pick the inductor, this should be a new thread.

You will need to debug your design by looking at the waveforms of the various pins of the IC and in the circuit. Based on what you describe and since you did your own layout, it sounds like noise is affecting the regulation. You can always order the EVM to get a known good circuit to test.

Power management

Power management forum

TPS61175 Inductor: DCR concerns