TPS65150: Boost converter issue

Davide Landi

Part Number: TPS65150

Tool/software:

Hi,

I'm prototyping a design to power a 7" LCD using the TPS65150 IC.

Immediately after VIN rises to 3.3V, the IC enters the fault condition due to a Buck Overvoltage (If I disable the fault protection, the Boost output reaches approximately 18V).

I tried a few different values for R5, but nothing changed between the attempts. What could be the cause of this unexpectedly high voltage? How can I fix it?

Thanks in advance.

Here is my schematic:

7 months ago

0 Steven Li 7 months ago

TI__Mastermind 23190 points

Hi Davide,

Our expert is currently out of office for Chinese New Year Holiday. He will reply to you after Feb.5 when back to office. Thanks for your understanding.

Best Regards,

Steven

0 Patrick Yao 7 months ago

TI__Mastermind 34780 points

Hi Davide,

What do you mean of the "Buck overvoltage"? TPS65150 only has boost converter.

Patrick

0 Davide Landi 7 months ago in reply to Patrick Yao

Prodigy 10 points

Hi Patrick,

I apologise for the typo, I meant Boost Overvoltage.

Davide

0 Patrick Yao 7 months ago in reply to Davide Landi

TI__Mastermind 34780 points

Hi Davide,

Could you please capture the voltage waveform of AVDD, VGH and VGL when power on the device?

Patrick

0 Davide Landi 7 months ago in reply to Patrick Yao

Prodigy 10 points

Hi Patrick,

Here are the waveforms you requested.

Thank you,

Davide

0 Patrick Yao 7 months ago in reply to Davide Landi

TI__Mastermind 34780 points

Hi Davide,

Is R5 = 136k or 13.6k?

Patrick

0 Davide Landi 7 months ago in reply to Patrick Yao

Prodigy 10 points

Hi Patrick,

R5 = 13.6k. Since I do not have a 13.6k resistor, in this prototype I'm using two 70k and one 22k resistors in parallel. At first, I used a 10k resistor, but nothing changed.

Davide

0 Patrick Yao 7 months ago in reply to Davide Landi

TI__Mastermind 34780 points

Hi Davide,

Did you connect the LCD panel? If so, will the IC start to work if the panel is disconnected?

Patrick

0 Davide Landi 7 months ago in reply to Patrick Yao

Prodigy 10 points

Hi Patrick

No, I didn't. I am a bit afraid to connect the panel because its AVDD max rating is 9.8V and the IC output goes to 18V. Can I simulate the LCD load with, for example, a resistor?

Thank you,

Davide

0 Patrick Yao 7 months ago in reply to Davide Landi

TI__Mastermind 34780 points

Hi Davide,

Will solder the C18 help with this issue?

Patrick

0 Davide Landi 7 months ago in reply to Patrick Yao

Prodigy 10 points

Hi Patrick,

I tried to solder the C18, but unfortunately it didn't help. The new waveforms are identical to the old ones.

Davide

0 Patrick Yao 7 months ago in reply to Davide Landi

TI__Mastermind 34780 points

Hi Davide,

Have you tried to switch the IC? Will all the ICs have the same issue?

Patrick

0 Davide Landi 7 months ago in reply to Patrick Yao

Prodigy 10 points

Hi Patrick,

Now I am a bit busy, but I will give it a try as soon as possible.

Davide

0 Patrick Yao 7 months ago in reply to Davide Landi

TI__Mastermind 34780 points

Hi Davide,

I will wait for your update.

Patrick

0 Davide Landi 7 months ago in reply to Patrick Yao

Prodigy 10 points

Hi Patrick,

I replaced the IC with a new one, but when I first turned it on I forgot to connect R5. After connecting R5, the new IC behaved exactly like the old one. Since the max boost output voltage is rated as 15V and on AVDD I read a 18V peak, is it possible that I damaged it? Tomorrow I will try again with another IC.

Davide

0 Steven Li 7 months ago in reply to Davide Landi

TI__Mastermind 23190 points

Hi Davide,

Our expert is currently out of office and will reply to you next Monday. Thanks for your understanding.

Best Regards,

Steven

0 Patrick Yao 7 months ago in reply to Davide Landi

TI__Mastermind 34780 points

Hi Davide,

It might be, please replace a new IC and try again.

Patrick

0 Davide Landi 6 months ago in reply to Patrick Yao

Prodigy 10 points

Hi Patrick,

Sorry for the late answer.

I replaced the IC and double checked every connection, but again nothing changed. AVDD goes to 18V and then the IC shuts down.

Just a note: in this prototype the EPAD is left floating.

Davide

0 Patrick Yao 6 months ago in reply to Davide Landi

TI__Mastermind 34780 points

Hi Davide,

The thermal pad should be connected to GND.

Patrick

0 Davide Landi 6 months ago in reply to Patrick Yao

Prodigy 10 points

Hi Patrick,

I'll design and order a through hole adapter with the EPAD connector and try again.

Thanks Patrick,

Davide

0 Patrick Yao 6 months ago in reply to Davide Landi

TI__Mastermind 34780 points

Hi Davide,

Noted.

0 Davide Landi 5 months ago in reply to Patrick Yao

Prodigy 10 points

Hi Patrick,

It took some time for the adapter to arrive. Unfortunately, the behavior of the IC did not change at all. After powering it on, AVDD goes straight up to 18V and then the IC shuts down.

Davide

0 Patrick Yao 5 months ago in reply to Davide Landi

TI__Mastermind 34780 points

Hi Davide,

Could you please capture the waveform of AVDD and CPI when power on the IC? In your schematic, is the ADJ cap C18 connected or not?

Patrick

0 Davide Landi 5 months ago in reply to Patrick Yao

Prodigy 10 points

Hi Patrick,

I confirm C18 is connected.

Here are the waveforms:

AVDD_CPI

Davide

0 Patrick Yao 5 months ago in reply to Davide Landi

TI__Mastermind 34780 points

Hi Davide,

Have you tried to increase the resistance of R4 and R5?

And it looks strange when AVDD ramps up, but CPI remains very low. Have you check the voltage drop on D2 and D3?

Patrick

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TPS65150: Boost converter issue