TPS54327: the switching frequency

Hirotaka Matsumoto

Part Number: TPS54327

Hi all

Would you mind if we ask TPS54327?
Please refer to the attachment file.(Vin=12V, Vout=1.5V)
20170418_TPS54327.pdf

Our customer changes the inductor value from 1.5uH to 2.2uH.
In this condtion, when the load changes from 1A to 2A, the switching frequency changes 200kHz upto 800kHz.
Vin and Vout are stable, is it common that the switching frequency changes 200kHz upto 800kHz?
Since there is no internal oscilator, the actual frequency may vary quite a bit.
It depends on "on time".

And then, when the inductor is 1,5uH, when the load changes from 1A to 2A, the switching frequency changes 500kHz upto 800kHz.
We think that this is normal operation.

Kind regards,

Hirotaka Matsumoto

over 7 years ago

0 Yuchang Zhang over 7 years ago

TI__Mastermind 18510 points

Hi Matsumoto-san,

Would you please upload your waveform for review? include SW and inductor current, Vout is better. and need zoom-in waveform as well.

Regards,

Yuchang

0 Hirotaka Matsumoto over 7 years ago in reply to Yuchang Zhang

Guru 27585 points

Yuchang san

Thank you for your reply.
We will get the wave form, so could you wait for a moment?

Kind regards,

Hirotaka Matsumoto

0 Yuchang Zhang over 7 years ago in reply to Hirotaka Matsumoto

TI__Mastermind 18510 points

Matsumoto-san,

OK, waiting for your test wavform.

Regards,
Yuchang

0 Hirotaka Matsumoto over 7 years ago in reply to Yuchang Zhang

Guru 27585 points

Yuchang san

We are sorry that we are late to get the test wave from our customer.
Could you wait for a moment?

Kind regards,

Hirotaka Matsumoto

0 Yuchang Zhang over 7 years ago in reply to Hirotaka Matsumoto

TI__Mastermind 18510 points

Matsumoto-san,

OK and Take it easy, Just follow your schedule.

Regards,

Yuchang

0 Hirotaka Matsumoto over 7 years ago in reply to Yuchang Zhang

Guru 27585 points

Yuchang san

We are sorry that we are late to get the wave form from our customer.
At the present, we surveyed the problem of the our customer's board.
the load of our customer's curcuit board change the current 1A to 2.5A 6us level.
So, we think it can't follow the current changing.
We quess that it require to insert the cap near the load.

Kind regards,

Hirotaka Matsumoto

0 Yuchang Zhang over 7 years ago in reply to Hirotaka Matsumoto

TI__Mastermind 18510 points

Matsumoto-san,
I think, For 54327, 1A to 2.5A 6us transient loading, should be no problem.
If you worry about something abnormal with the E-load, you can measure Iout with current probe to monitor the loading current.
and by the way, It's normal that the frequency will change during loading change, but in stable loading, the Frequency should be stable as well.

Regards,
Yuchang

0 Hirotaka Matsumoto over 7 years ago in reply to Yuchang Zhang

Guru 27585 points

Yuchang san

Thank you for your support always!
On the next stage, we are survey the wave form using our customer board.
We will feedback you later.

Kind regards,

Hirotaka Matsumoto

Power management

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TPS54327: the switching frequency