TPS92640: TPS92640　datasheet　Fs: Switching Frequency

Masa_0000

Intellectual 885 points

Part Number: TPS92640

Hi Everybody!

I have a question about "TPS92640: datasheet Fs: Switching Frequency.

SNVS902A.pdf
TPS92640 datasheet wrote:
”nearly constant switching frequency”

But follow the output current, "switching frequency" is moved widely.

My question is followings :

Q1: Please let me know why move "switching frequency" (how the method of this control).

Q2: Please let me know the method of stop moved "switching frequency".

In case of mainly light load, this is my issue.
It is difficult at "counterplan of EMI"

My customer setting is followings:
1)Fs:200kHz(R_on:31k,C_on:470pF )
2)Vin:48V
3)Iout:0.65A
4)Vout:4V
5)LED:1pcs Vf:2.7~3.2V @0.2A~1.8A

Best Regards
Shing

over 5 years ago

0 Irwin Nederbragt over 5 years ago

TI__Mastermind 28655 points

Hello Shing,

This is in the datasheet. Ron controls the current going into the Roff capacitor. Vout divider controls where the trip threshold is.

What are the resistors from Vout to the Vout pin? This is what sets the trip threshold for the ON-time control.

What is Vout, you have 4V but show an LED that is 2.7V to 3.2V.

Efficiency will also cause variations and a low output voltage with high input voltage will not be as efficient.

Your Questions are related to the above, at one LED the switching frequency will vary quite a bit.

Best Regards,

0 Irwin Nederbragt over 5 years ago in reply to Irwin Nederbragt

TI__Mastermind 28655 points

Hello Shing,

I haven’t heard back from you, I’m assuming you were able to resolve your issue.
If not, just post a reply below (or create a new thread if the thread has locked due to time-out)

Best Regards,

0 Masa_0000 over 5 years ago in reply to Irwin Nederbragt

Intellectual 885 points

Hello Irwin-son!

I have to apologize to you.
I have to spend a time of this customer reconfirm this issue.
But I'll be a speedy response.

If you could share the schematics and Oscilloscope capture with E-mail, then please let me send your E-mail.

Best Regards
Shing

0 Irwin Nederbragt over 5 years ago in reply to Masa_0000

TI__Mastermind 28655 points

This is taken to email, off of e2e.

Best Regards,

0 Masa_0000 over 5 years ago in reply to Irwin Nederbragt

Intellectual 885 points

Hi Irwin-san

Thank you for your cooperation.
And thank allow the e-mail.
I'd like to next step.

Please tell me what do I do.

Best Regards
Shing

0 Irwin Nederbragt over 5 years ago in reply to Masa_0000

TI__Mastermind 28655 points

This is taken to email, off of e2e.

Best Regards,

Power management

Power management forum

TPS92640: TPS92640　datasheet　Fs: Switching Frequency

Power management

Power management forum

TPS92640: TPS92640 datasheet Fs: Switching Frequency

TPS92640: TPS92640　datasheet　Fs: Switching Frequency