TPS61194: TPS61194 turns off when PWM is less than 40%

vlad123 vlad321

Part Number: TPS61194

The TPS61194 operates at 1300 kHz. Input voltage 12 volts, output 21 volts, output current 380 ma. I deliberately used 2 and not 3 capacitors of 10 microfarads.

I have a problem when the TPS61194 stops working after a while and does not give an error signal (FAULT to logical 1). TPS61194 generates pulses on the sw pin. But when the pwm is less than 40%, the pulses disappear and the microcircuit stops working. This happens after 1-20 minutes when pwm is below 40%. Only closing VDDIO / EN to logical 0 helps. Pwm signal and use with a frequency of 2 kHz.

I found a position where the TPS61194 does not turn off. The PWM signal does not go directly from the microcontroller pin, but through the BSS123 transistor, which inverts the signal. And when I connected the pwm pin of TPS61194 directly to the microcontroller, the TPS61194 always works.

What could be the reason?

https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/196/0312.TPS61194.7zIn the archive I load the scheme.

over 4 years ago

0 Yuting Shao over 4 years ago

TI__Genius 13001 points

Hi,

I can't view your schematic. Could you please reload it? Thanks!

BR,

Robin

0 vlad123 vlad321 over 4 years ago in reply to Yuting Shao

Prodigy 150 points

https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/196/4682.TPS61194.7z

0 Yuting Shao over 4 years ago in reply to vlad123 vlad321

TI__Genius 13001 points

Hi,

I'll reply you later.

BR,

Robin

0 vlad123 vlad321 over 4 years ago in reply to Yuting Shao

Prodigy 150 points

I seem to have solved the problem.

At first I turned on the enable signal, and after 400ms I turned on the input voltage of 12 volts. Now I did the opposite, and tps1194 works stably. Is this even possible?

And I also found an inaccuracy in my scheme. The CFB capacitor should be about 8 pF because the tps61194 operates at 1.3MHz. Tell me, can there be problems if I have a CFB capacitor of 15pf and a frequency of 1.3MHz?

0 Yuting Shao over 4 years ago in reply to vlad123 vlad321

TI__Genius 13001 points

Hi,

Generally, enabling firstly is a more proper choice. As for Cfb, I don't think it will result in the phenomenon you saw.

This device's oscillator is sensitive to noise, especially noise from VDDIO. It may lead to abnormal operation. It's hard to repeat and occurs suddenly.

Please make sure that the VDDIO power rail is stable and without noise.

BR,

Robin

0 vlad123 vlad321 over 4 years ago in reply to Yuting Shao

Prodigy 150 points

It looks like the problem is still there. The switching sequence is probably not the main problem, because the display still goes out after.

At the moment when tps1194 turns off, VOUT = VIN and the signal on the sw pin disappears. Fault pin is always 3.3 volts. As if there is no problem.

Signals en and pwm are present.

Oscillograms in the archive.

https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/196/61194.7zHow can the problem be diagnosed?

0 Yuting Shao over 4 years ago in reply to vlad123 vlad321

TI__Genius 13001 points

Hi,

Could you please change the resister divider to make sure 12Vx(R2/(R1+R2))<1.44V? It may help for your issue.

BR,

Robin

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TPS61194: TPS61194 turns off when PWM is less than 40%