LM3481: Compensation

user5861925

Part Number: LM3481
Other Parts Discussed in Thread: LM5155

Hi:

The product I designed USES LM3481,COMP Pin as Compensation Pin,Rc= 22.6k, which is not normal resistance. How is the resistance value set?Is there a formula?thank you.

Sunny

over 6 years ago

0 Garrett Roecker over 6 years ago

TI__Mastermind 21720 points

Hi Sunny,

Thanks for reaching out with your question. To summarize, are you asking how to calculate the control loop compensation values?
If so please provide the application specifications (VIN range, VOUT, IOUT, Fsw) and the schematic.

Thanks,

Garrett

0 user5861925 over 6 years ago in reply to Garrett Roecker

Intellectual 570 points

Hi Garrett:

The following are the specifications and schematic diagram of the application:

Vin:12V, Vout :24V , Iout:2A , Fsw:100KHZ

0 Garrett Roecker over 6 years ago in reply to user5861925

TI__Mastermind 21720 points

Hello Sunny,

Do you have a higher resolution image of the schematic? I cannot read the part values or the inductor part number.

Thanks,

Garrett

0 user5861925 over 6 years ago in reply to Garrett Roecker

Intellectual 570 points

Hi Garrett:

The schematic diagram is as follows:

0 Garrett Roecker over 6 years ago in reply to user5861925

TI__Mastermind 21720 points

Hi Sunny,

The compensation resistor value can be calculated using the following equation. This is similar to the calculations done in the LM5155 application note for designing a boost controller

Fcross is the desired cross over frequency value and is typically less than 1/5th the right-half plane zero frequency. The value of RCOMP can be shifted to a standard value without having much impact on the circuit.

Please let me know if you have any questions.

Thanks,

Garrett

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LM3481: Compensation