TPS61087EVM-317: TPS61087

5141020

Prodigy 160 points

Part Number: TPS61087EVM-317
Other Parts Discussed in Thread: TPS61087

Hi,

I'm using TPS61087EVM board for 15V output (input 3V) load 40ohm

and I added 18k resistor to FB pin and trying to regulate the ouput voltage with voltage to 18k ohm from 1-2V

Regulation works but the output has ripple about 500mV. I there any way to reduce the output ripple?

thanks answer

over 4 years ago

0 Helen chen over 4 years ago

TI__Mastermind 40080 points

Dear Sir,

How did you add the external voltage and how did you connect it? Is it a very clean voltage?

0 5141020 over 4 years ago in reply to Helen chen

Prodigy 160 points

Dear Helen,

I put voltage from adjustable power supply with 18kohm resistor and the result of 10V output at 1.58V on FB pin

0 5141020 over 4 years ago in reply to 5141020

Prodigy 160 points

Output voltage 10V +- ripple as on oscillograph

Input on feedback over additional 18k ohm resistor 1.58V

with board TPS61087evm-317 @650kHZ

Any help are welcome

Thanks

0 Helen chen over 4 years ago in reply to 5141020

TI__Mastermind 40080 points

Dear Sir,

You need to add a AC filter before the 18K resistor. Or the injected voltage is not clean enough.

0 5141020 over 4 years ago in reply to Helen chen

Prodigy 160 points

I have add capacitors 10n 100n and 100p before 18k ohm but didn't help much about 50-100mV.

Any suggestion to add to FB divider any capacitor or is the problem that FB trying to change the output voltage?

I'm trying to do this because I want to regulate output voltage of boost converter with DAC

Do you have any solution already how to change the ouput voltage of TPS61087 with DAC or I doing somethingwrong?

Thanks in advance

0 Helen chen over 4 years ago in reply to 5141020

TI__Mastermind 40080 points

What is the R before 10n 100n and 100p cap?

0 5141020 over 4 years ago in reply to Helen chen

Prodigy 160 points

I have put 1k

to cutoff 1.6K, 16K

0 Helen chen over 4 years ago in reply to 5141020

TI__Mastermind 40080 points

thanks for the update!

Does the RC filter's GND connected to the GND of the R3's GND on the EVM board?

0 5141020 over 4 years ago in reply to Helen chen

Prodigy 160 points

Yes connected to the GND of EVM.

Thank you,

0 Helen chen over 4 years ago in reply to 5141020

TI__Mastermind 40080 points

Did you check the inject source voltage, is it clean?

0 Helen chen over 4 years ago in reply to 5141020

TI__Mastermind 40080 points

Did you check the inject source voltage, is it clean?

0 5141020 over 4 years ago in reply to Helen chen

Prodigy 160 points

Hi,

clean DC voltage in feedback.

Do you recommending any xpF capacitor parallel with feedback resistors?

0 Helen chen over 4 years ago in reply to 5141020

TI__Mastermind 40080 points

Its strange.

Please try to change Rcomp=R1 to a smaller value like 2k to check whether it could be helpful.

0 Helen chen over 4 years ago in reply to Helen chen

TI__Mastermind 40080 points

Dear Sir,

Did you ever try to change the Rcomp to check whether it could be helpful?

0 5141020 over 4 years ago in reply to Helen chen

Prodigy 160 points

Hello Helen,

I have tried but I can't say that is better now. I'm not sure anymore what's going worng way. The same concept with external FET+ DC/DC driver works better but is more expensive solutions....

thanks for help

0 Helen chen over 4 years ago in reply to 5141020

TI__Mastermind 40080 points

Dear Sir,

Another thing you need to try is to try to increase the resistance of the 18k added resistor, you can increase it to 100k ohm, it will be much better since the injected signal can be a more smaller signal, hence not easily cause the stability issue.

Power management

Power management forum

TPS61087EVM-317: TPS61087