TPS54302: Inductor Selection

Sadanori Kato

Part Number: TPS54302

Hi,

According to TPS54302 data sheet, the minimum value of the output inductor(Lmin) is calculated with the equation 8 as follows.
If calculating Lmin under the following condition, 8.65uH will be given.

- Condition
Vout     = 1.8V
Vin(max) = 5.5V
Kind     = 0.35
Iout     = 1A
Fsw      = 400kHz
Lmin     = 8.65uH

On the other hand, 3.3uH will be given if using WEBENCH Power Designer. So, could you please tell me which result is correct?

Best regards,
Kato

over 5 years ago

0 Lishuang Zhao over 5 years ago

TI__Expert 7500 points

Hi Kato,

The Iout in the equation is the IC's max Iout not the application output current.So you should use Iout=3A to calculate.

Thanks,

Lishuang

0 Sadanori Kato over 5 years ago in reply to Lishuang Zhao

Guru 36530 points

Hi Lishuang-san,

Thank you for your prompt reply.

The maximum output current which is actually used is 1A. Why should IOUT be 3A?
Is my understanding correct that it is necessary to consider the current limit?

Best regards,
Kato

0 Lishuang Zhao over 5 years ago in reply to Sadanori Kato

TI__Expert 7500 points

Hi Kato,

The internal loop parameters design is based on 3A calculated L and Cout interval range. If you use 1A to calculate L, the system may be unstable. And what's more, the 1A calculated L is large, which means the DCR will be higher, so the loss will be higher.

Thanks,

Lishuang

0 Sadanori Kato over 5 years ago in reply to Lishuang Zhao

Guru 36530 points

Hi Lishuang-san,

Thank you for the information.

I understand.

Best regards,
Kato

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TPS54302: Inductor Selection