LM5175: LM5175PWPR

prabha Karan

Part Number: LM5175

Hello,

I designed the schematic from reference design for LM5175PWPR (Buck Boost ) converter. I used exactly same components and values that mentioned in the reference design . I have fixed RFbt value is 453K ohm and Rfbb value is 20K ohm as per the recommendation. If I give Input voltage is 14V means I getting 13.5V as output and If I give 7V input means I get only 6.5V only.

But My required output voltage is 19V/3Amps fixed even though input may vary from 14V to 15V getting from the battery my output should be constant 19v/3A for laptop charge. So please suggest me sort out this problem as soon as possible. Please see the attached schematic and advise me where I need to change the values. Its an urgent task for me.

PLease email me on- info@kentronicsengineering.comSchematic Prints_Boost.pdf

over 8 years ago

0 Youhao Xi over 8 years ago

TI__Guru* 78400 points

Hi Prabha,

Thank you for considering the LM5175. It seems your circuit's boost leg did not work. Would you please check your circuit connections on your board, and measure the SW1 and SW2 waveforms?

Thanks,
Youhao Xi, System and Applications Engineering, APP-BMC-BCS, TI

0 prabha Karan over 8 years ago in reply to Youhao Xi

Prodigy 120 points

Hello Mr.Youhao Xi,
Means I need to check the voltage in Cboot1 and Cboot2 capacitor? Right now I dont have scope I can check through multimeter only.

0 prabha Karan over 8 years ago in reply to prabha Karan

Prodigy 120 points

Hello,
Voltage shows in SW1 -14.2V ,SW2-14.22V. Voltage between Dboot1 & Cboot1- 13.97V and Voltage between Dboot2 & Cboot2-14.7V.

0 Youhao Xi over 8 years ago in reply to prabha Karan

TI__Guru* 78400 points

I need to see if your boost leg is switching or not. These DM readings do not help much. Please get an oscilloscope and measure the switch node waveforms.

0 prabha Karan over 8 years ago in reply to Youhao Xi

Prodigy 120 points

Hello Mr.Youhao Xi,
Right now I cannot get the oscilloscope and also it take more time (minimum 15 to 30 days). So please suggest me the alternate ways that if the boost leg is not switching means what I need to do and if it is switching means what I need to do. So I can try to solve the problem as soon as possible.

0 prabha Karan over 8 years ago in reply to prabha Karan

Prodigy 120 points

I am waiting for your advice.

0 Garrett Roecker over 8 years ago in reply to prabha Karan

TI__Mastermind 21720 points

Hi Prabha,

Please use the quick-start calculator to check the component selection for your design. This should help to make sure that your components are correct. Please also ensure that the layout follows the guidelines described in the datasheet.

Note that it is impossible to get a good idea of what might be causing the issue if an oscilloscope is not used. A DMM cannot provide the amount of detail that is needed to gain any insight into what might be causing the issue.

Thanks,

Garrett

0 prabha Karan over 8 years ago in reply to Garrett Roecker

Prodigy 120 points

Hello Mr. Garrett,
I have noticed that many component values are changed from the reference schematic which is generated by webench design and notable changes is ISNS+ &- Pin is shorted and connected to ground in reference design but in the calculator its connected to the output terminal. Please advice me which is correct.

0 prabha Karan over 8 years ago in reply to prabha Karan

Prodigy 120 points

Hello,
Can you send me the schematic file for input 14.4V and 19V Output altium file for me

0 Garrett Roecker over 8 years ago in reply to prabha Karan

TI__Mastermind 21720 points

Hi Prabha,

The when the ISNS+ and ISNS- pins are connected to ground this just means that the average current limit on the output is not activated. This is described in section 8.3.6 of the datasheet. If you do not need this feature please leave them connected to ground. Please follow the quickstart calculator to check the other component values.

Are you asking for the Altium schematic and layout for the EVM?

Thanks,

Garrett

0 prabha Karan over 8 years ago in reply to Garrett Roecker

Prodigy 120 points

Hello Mr. Garrett,
Yes Please send me the altium schematic file and pcb file for input 14.4 V and 19V/3 Amps otput.

0 Garrett Roecker over 8 years ago in reply to prabha Karan

TI__Mastermind 21720 points

Prabha,

If you created your design based on the design example in the datasheet then the LM5175EVM can be used as a good reference for layout. Please let me know if this board is one that you are requesting the Altium files for.

Thanks,

Garrett

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LM5175: LM5175PWPR