TPS62067: Maybe periodically about 100ns turn on delay for the high side FET

Yoshwa

Expert 4050 points

Part Number: TPS62067
Other Parts Discussed in Thread: TPS62097, TPS62822, TPS62065,

Hi, team

Customer inquired how to reduce output ripple.

So, I asked to send operational waveforms at some key points.

The attached SW-pin waveform was sent for the sample with output ripple issue.

There is turn on delay of about 100ns for the high-side switch on.

What kind of problems are there?

over 6 years ago

0 Chris Glaser over 6 years ago

TI__Guru*** 142880 points

Hi Yoshwa-san,

There was no attachment.

And this is a very old device which does not tolerate a large/strong output filter. Newer 2A devices, which generally have lower ripple, include the TPS62097 and TPS62822.

0 Yoshwa over 6 years ago in reply to Chris Glaser

TI__Expert 4050 points

Chris-sann,

Thanks for your prompt response.

I attached the waveform.

Yoshifusa Wada

TPS62067 SW-pin issued sample.pdf

0 Chris Glaser over 6 years ago in reply to Yoshwa

TI__Guru*** 142880 points

Thank you for sending but this is a waveform of the SW node. I thought the reported problem was output ripple?

What is the Vin, Vout, Iout used in that waveform? Does this happen on one device/board or all boards? Is it periodic or random (occurs rarely)?

0 Yoshwa over 6 years ago in reply to Chris Glaser

TI__Expert 4050 points

The attached 3.3Vout waveform was only sent.

Vin is 5.0V and 3.3V load current was about 200mA to 300mA.

L=1.2uH,

Cout=22uF + 10pF,

Cin=10uF

Can you estimate issues based on only this data?

Customer is going to use PWM mode for minimize vout ripple.

He had already confirmed small ripple features using his board at 100mA and 0.5A load conditions.

TPS62067 3_3VOUT ripple.pdf

TPS62067 33 ohm load.pdf

Yoshifusa Wada, CS Japan

0 Chris Glaser over 6 years ago in reply to Yoshwa

TI__Guru*** 142880 points

Hi Wada-san,

Thanks for sending.

The TPS62067 has no forced PWM mode option. Will he use TPS62067 or TPS62065? I recommend using a newer device, like TPS62097.

The latest waveforms show PFM mode, not forced PWM mode.

These lighter loads are close to the PFM/PWM boundary.

What are the FB resistor values?

Can he also test with the recommended 1 uH coil?

0 Yoshwa over 6 years ago in reply to Chris Glaser

TI__Expert 4050 points

Chris sann,

Many thanks for your comments.

I had passed your recommended TPS62097 to customer.

However, customer is considering replacing to TPS62065 because of direct replacing.

TPS62067 is my mistake.

No, he did not test for the1 uH.

FB resistors are 150 kohm and 680 kohm for 3.3 V out.

Best regards,

Yoshifusa Wada

Power management

Power management forum

TPS62067: Maybe periodically about 100ns turn on delay for the high side FET