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TPS65145: TPS65145 efficiency

Moshe Levy
Prodigy 230 points
Part Number: TPS65145

Hello

I am using TPS65145 with output current of 25mA. per TPS65145 datasheet figure 12, the efficiency is ~72%.

Reading in the datasheet page 13 section 8.2.2.1.1 it is stated that the efficiency is inductor dependent. The dependency is influenced by:

- DCR dependent: The lower the DCR. The better the efficiency.

- Form Factor dependent: The larger the form factors the better the efficiency (2% to 10%).

but, looking at Table 2 (page 14) - "Inductor Selection".... looking at 3.3uH inductors and arrange them by form factor...smaller to higher:

3.3 µH           Sumida             CDRH2D18/HP 3R3          3.2 × 3.2 × 2            1.45 A,      69 mΩ

3.3 µH           Sumida             CDPH4D19 3R3                5.1 × 5.1 × 2            1.5 A,         26 mΩ

3.3 µH           Coilcraft            DO1606T-332                    6.5 × 5.2 × 2            1.4 A,         120 mΩ

3.3 µH           Coilcraft            LPO6610-332M                 6.6 × 5.5 × 1            1.3 A,         160 mΩ

The DCR is not reduced with a larger form factor as written in the datasheet.

Can you explain why? Is it because of different inductor material?

  • 0
    TI__Mastermind 18550 points

    Hello Moshe,

    Inductor DCR impacts efficiency because power losses in the inductor are proportional to DCR.

    As for DCR and inductor size, given same inductance value, in general it makes sense that DCR should be lower for bigger sized inductors since they can use a thicker wire or bigger printed metal structure. But there can be other contributing factors such as core material and type of metal structure/wire used etc. I would suggest to contact inductor manufacturers to get further guidance in this respect as we are not experts in this regards.

    Kind Regards,

    Liaqat