BQ25758: Inductor Design for Buck Boost Converter for USB EPR Designs up to 48V/5A/240W

Saunak Bhalsod2

Prodigy 50 points

Part Number: BQ25758
Other Parts Discussed in Thread: BQ25756, TPS62933

Tool/software:

Hi TI,

I am designing the power converter based on BQ25758 the spec is as below

VIN=19.5V+/-5%

VOUT= USB PD EPR voltages (5V, 9V, 15V, 20V, 28V, 36V, 48V)

IOUT=5A

Switching Frequency = 450kHz.

For this I am using inductor as IHLP6767GZER5R6M11 which has below spec

Inductance = 5.6uH+/-20%

ISAT= 21A IDC_heat= 28A

DCR = 4.44mohm

I have used BQ25756 Design Calculator from TI and based on that I have chosen the inductor. However, In EVM and Datasheet the inductor chosen is 10uH, 22mohm.

I want to know can you please confirm whether the inductor which I am using is okay or not?

over 1 year ago

0 Ethan Galloway over 1 year ago

TI__Mastermind 30915 points

Hello Saunak,

That inductor should work for your application.

I would also recommend adding an external gate drive if you aren't already. Going from 19.5V to 48V will incur a lot of losses. Using an ideal converter as an example, you'll have 12.3 amps going into the input of the converter at 48V and 5A.

Best Regards,
Ethan Galloway

0 Saunak Bhalsod2 over 1 year ago in reply to Ethan Galloway

Prodigy 50 points

Hi Ethan, I agree with you. I am using TPS62933 based Buck Converter to generate 12V/3A Gate Driver Supply from 19.5V Input as it is mentioned in datasheet of BQ25758

I am connecting 12V Gate Driver Supply to DRV_SUP pin. I feel this will work, please let me know your view on this

0 Ethan Galloway over 1 year ago in reply to Saunak Bhalsod2

TI__Mastermind 30915 points

Hello Saunak,

Yes, an external gate drive supply of 12V should work with the IC.

Best Regards,
Ethan Galloway

0 Saunak Bhalsod2 over 1 year ago in reply to Ethan Galloway

Prodigy 50 points

Thanks Ethan

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BQ25758: Inductor Design for Buck Boost Converter for USB EPR Designs up to 48V/5A/240W