TPS4H000-Q1: Start up behavior

Kuramochi Tadahiko

Guru 28715 points

Part Number: TPS4H000-Q1

Hi,

My customer is evaluating the TPS4H000-Q1 on their board.

Even though IN=Low, OUT voltage appears when VS rising up as below;

Does it caused by the TPS4H000 ?

If not, I will request the customer to check another circuit.

Best Regards,

Kuramochi

over 6 years ago

0 Elizabeth Higgins over 6 years ago

TI__Genius 16145 points

Hi Kuramochi-san,

Thanks for reaching out on E2E!

Could you send a schematic? If you prefer not to send it through this platform, you can email me at e-higgins@ti.com

Thanks,

Elizabeth

0 Kuramochi Tadahiko over 6 years ago in reply to Elizabeth Higgins

Guru 28715 points

Elizabeth-san,

Thank you for your reply.

I checked that this behavior happens on my EVM as below.

Condition: THER=DIAG_EN=HIGH, No load

Is this caused by the device?

Best Regards,

Kuramochi

0 Elizabeth Higgins over 6 years ago in reply to Kuramochi Tadahiko

TI__Genius 16145 points

Kuramochi-san,

Could you specify what you mean by no load? Do you have a Hi-Z load, open circuit load, short circuit load, etc?

Could you also elaborate on how the waveform is being probed?

Additionally, if you want open load detection in the off state, we recommend using a pull-up resistor across the output to the input, as shown in figure 30 of the datasheet.

Best Regards,

Elizabeth

0 Kuramochi Tadahiko over 6 years ago in reply to Elizabeth Higgins

Guru 28715 points

Elizabeth-san,

>Could you specify what you mean by no load? Do you have a Hi-Z load, open circuit load, short circuit load, etc?

Open circuit load.

I was not connecting anything to out pin.

>Could you also elaborate on how the waveform is being probed?
I used the "N2863B" with not GND springs but normal GND cables.

Can you confirm it on your EVM? You should be able to observe same waveforms easily.

Best Regards,

Kuramochi

0 Kuramochi Tadahiko over 6 years ago in reply to Kuramochi Tadahiko

Guru 28715 points

Elizabeth-san,

Could you see this behavior on the EVM?

This is caused by the THS4H140-Q1, isn't it?

Best Regards,

Kuramochi

0 Elizabeth Higgins over 6 years ago in reply to Kuramochi Tadahiko

TI__Genius 16145 points

Kuramochi-san,

I apologize for the delay. We do not have any TPS4H000-Q1 EVMs in house. We have ordered some and they are in the process of getting here. In the meantime, I reached out to design and this issue could be due to current leakage or coupling during supply ramp-up. If OUT has a certain load (such as 10kohms), then OUT will stay low when Vin is ramped to 24V. The resistor will prevent OUT to increase due to the leakage or coupling during supply ramp-up. You can see if this solves the issue. Also, I am a little confused by your last message. Did you mean to say TPS4H000-Q1 instead of THS4H140-Q1?

Best Regards,

Elizabeth

0 Kuramochi Tadahiko over 6 years ago in reply to Elizabeth Higgins

Guru 28715 points

Elizabeth-san,

Sorry for delay.

>Did you mean to say TPS4H000-Q1 instead of THS4H140-Q1?

We can look this phenomenon with both devices .

How is your progress of evaluation?

Best Regards,

Kuramochi

0 Kuramochi Tadahiko over 6 years ago in reply to Kuramochi Tadahiko

Guru 28715 points

Elizabeth-san,

How is your progress of evaluation?

My customer is waiting for your reply

Best Regards,

Kuramochi

0 Elizabeth Higgins over 6 years ago in reply to Kuramochi Tadahiko

TI__Genius 16145 points

Kuramochi-san

Apologies for the delay. From your waveform, it appears the current only reaches 290mV instead of 2.9V. I determined this by the increment in the y-axis defined for OUT1 (blue waveform) as 100mV per division instead of the IN1 (pink waveform) which is 1V per division. Is 300mV an issue for you?

Best Regards,

Elizabeth

0 Elizabeth Higgins over 6 years ago in reply to Elizabeth Higgins

TI__Genius 16145 points

Kuramochi-san,

If your use case is to have open load detection with enable low, you need a pull up resistor.

When using a pull up resistor, such as 10kohms, you will get the waveforms as shown below where the open load fault is reported out and Vout follows Vin

If you do not want Vout to increase under these conditions, you must add an output load, less than the pull-up resistor. Due to the output load, the output voltage will be pulled down, as shown in the waveform below with a resistive output load of 300 ohms.

Best Regards,

Elizabeth

Please click "This resolved my issue" button if this post answers your question.

0 Kuramochi Tadahiko over 6 years ago in reply to Elizabeth Higgins

Guru 28715 points

Elizabeth-san,

Thank you for your confirmation.

Is this pulse caused by leak current from Vs until enable internal circuit?

Best Regards,

Kuramochi

0 Elizabeth Higgins over 6 years ago in reply to Kuramochi Tadahiko

TI__Genius 16145 points

Kuramochi-san,

I have not been able to recreate your exact situation. Only the waveforms I have shown previously. Perhaps it is best that you email me directly at e-Higgins@ti.com with any relevant information or data on the system and we can set up a call to learn more about the conditions of your system to better support your inquiry.

Best Regards,

Elizabeth

0 Kuramochi Tadahiko over 6 years ago in reply to Elizabeth Higgins

Guru 28715 points

Elizabeth-san,

I had misunderstood.

I think that you are zooming out observation range too much.

Can you zoom VOUT to 100mV/DIV?

Best Regards,

Kuramcohi

0 Elizabeth Higgins over 6 years ago in reply to Kuramochi Tadahiko

TI__Genius 16145 points

Kuramochi-san,

Can you confirm that your output voltage waveform is reaching a max of 300mV and not 3V?

Best Regards,

Elizabeth

0 Cameron Phillips over 6 years ago in reply to Elizabeth Higgins

TI__Genius 12410 points

Hello,

Do you still have this issue or can we close the thread?

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TPS4H000-Q1: Start up behavior