TPS65310A-Q1: Detailed Design about BUCK1 Controller,How to choose Output inductor?

user5795039

Part Number: TPS65310A-Q1

Dear All:

In the datasheet, it tells us when we choose the Output inductor about BUCK1 Controller we shoud follow the condition : L=410*Rs， so what the condition sourse from and why the coeficient is 410?

best regards

over 6 years ago

0 Abhinav.Sharma over 6 years ago

TI__Genius 9375 points

Hi User,

I have assigned this post to Murthy who supports this device directly so please allow for some delay in answering your question as he will not be back until January 2nd.

Thank you,

Abhinav.

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For more information on Multi-Channel Power Management ICs visit www.ti.com/PMIC

0 Brian Berner over 6 years ago

TI__Mastermind 30310 points

Hello,

I have assigned this thread to the expert on the TPS65310A-Q1 device and he will respond as soon as possible.

Note that the time from Dec. 24th through Jan. 2 is an important US Holiday period, and answers to questions may be delayed.

0 Krishnamurthy Hegde over 6 years ago in reply to Brian Berner

TI__Expert 8730 points

Hi,

"Rs" is sense resistor value. So, first Rs needs to be calculated based on your maximum load current. Then inductor needs to be calculated.

Regards,

Murthy

0 user5795039 over 6 years ago in reply to Krishnamurthy Hegde

Prodigy 190 points

Dear Murthy ：

Thank you for your reply, but I want to know in the equation "L=410 Rs " why the coefficient is 410 ?

Best Regards

0 Krishnamurthy Hegde over 6 years ago in reply to user5795039

TI__Expert 8730 points

Hi,

The coefficient value of 410 is coming from device internal design specifications considering the optimum slope compensation.

Regards,

Murthy

0 user5795039 over 6 years ago in reply to Krishnamurthy Hegde

Prodigy 190 points

Dear Murthy:

Thank you for your reply. But I want to know that if the coefficient 410 must be meet? If I chose the inductor value is not meet the equation 3, what is the problem will I meet?

best regards

0 Krishnamurthy Hegde over 6 years ago in reply to user5795039

TI__Expert 8730 points

Hi,

For choosing the inductor , calculate the theoretical value based on this equation and then choose the nearest available inductor in the market and it should work for you. For example, if you get 5.5uH based on your calculation, you can choose 4.7uH or 6.8uH and both should work.

Usually for duty cycle less than 50%, risk of sub harmonic oscillation issues due to slope compensation is very less. Also if you choose the inductor with a value slightly greater than the calculation should work. But please validate and make sure that you dont see sub harmonic oscillations (PH1 jitter) on your board for the inductor you choose.

Regards,

Murthy

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TPS65310A-Q1: Detailed Design about BUCK1 Controller,How to choose Output inductor?