LMR64010: I made a circuit along the text but it does not work well.

Hi Kondo,

What do you mean "The output voltage stabilizes when 12V is 2V IN". What's the load current?
Do you have any waveform?

Do I need to put on load resistance?

Hi Kondo,

It is not necessary. Can you share the layout, key waveforms to help me analyze?

The layout is the same as the attached file.

What piont of the waveforms should I show?

Hi Zack,

Please reply me for my answer.

Why does not stable when the input is moving?

Hi Kondo,

I cannot see your layout file. The two files you attached are the same schematic. The schematic looks correct.
Please show some waveform when Vin =3.3 V like you said, capture SW, Vin, Vout waveforms with oscilloscope.

Hi Zack,

I attached the waveform.

TEK00064 : 3.3vin

TEK00065 : 12vout

TEK00066-68 : SW

Please analyze those.

I sent one photo incorrectly.

This is a 3.3vin picture. By the way, I am in Japan. Where are you now?

Hi Kondo,

Can you give some description of each graph next time? Otherwise I don't what do they mean. You upload five graphs but telling me 3 below.
I guess the first two picture is Vout, last 3 are SW, correct?
Vout now is 12V. What's the load current now? Can you also measure Vin pin waveform?
Please use single mode to capture SW pin waveform to get a clearer waveform. It seems SW is out of order.

Hi Konda,

I'm in China.

I'm sorry.

The first two are out, the second is sw, and the retransmission is in.

The load current is 50mA.

I sent one single shot.

This should not have failed, because I just replaced it.

What is the cause of failure?
I am only making this along WEBENCH.

webench.ti.com/.../46

Hi Kondo,

SW pin waveform shows the system is unstable. Could you try to decrease capacitor Cf to 100pF?

I replaced Cf with 10 pF.

SW seems to move the base up and down.

The out voltage changes with load change and is not stable.

Excuse me.
I replaced Cf with 100pF, not 10pF.

What is the ideal waveform?
Why can't it make regulation?

Hi Kondo,

Ideally, the device duty cycle is quite stable, not like your board.
What's the output voltage at no load and 50mA load current condition seperately?

I do not understand well what it means？

I will send you a picture of no load.

I just sent a photo of 50mA load.

I mean what's the output voltage when Io is 50mA and what's the output voltage when Io is 0?

No load is the waveform I sent most recently.
The waveform is not beautiful.
Is my construction not good?

Hi Kondo,

The Vout waveform looks quite stable even though duty cycle changes every cycle. Please use DMM to measure Vout DC value at no load & 50mA load condition separately.

Zack,

OK, I will check it tomorrow.

kondo

Hi Kondo,

Any new finding?

I will send the waveform to you.

This is getting better, but the voltage drops slightly depend on the load.

Is it normal?

Hi Kondo,

Please see below picture. I use EVM and all component parameters are the same with what you provided. The Vout keeps stable at 12V at no load condition and 50mA load current condition.

Can you share the layout of your board?

current transmitter.pdf

Zack、

I sent my PDF sch. to you.

Can you open this?

I mean PCB layout file, not schematic.

Can you share the PCB layout file. Sometimes bad layout will affect the stability.

Zack,

Should I send a photo of the test board?

The wiring is complicated.

Kondo

Zack,

My board is not formal yet, and not PCB.

Kondo