TPS62175: TPS62175 having startup issues with >300mA load.

Hi Jagdish,

You are likely triggering the reduced current limit during startup, as explained in section 8.4.1 of the D/S. You could measure the inductor current to confirm this.

Hi Chris,

Sorry for replying late as I was out of office. Please see attached waveforms with 7.9E & 13.5E. The difference is there is some current glitch with 13.5E when output voltage reaches 3.4V which is absent in case of 7.9E. These waveforms are similar to ones as shown in datasheet. 

=> So if you think IC is going into startup current limit then I don't understand the reason of marketing this IC as 500mA regulator. I think any IC is required to bear the startup of max load for which it is defined. 

=> What is the solution to this issue, kindly advice.

Regards,

jagdish

Hi Chris,

Additional request request by Omar, I can't locate that reply in this thread so I reply to you,

1. Please find attached schematic section of 3.4V section.

2. Also we are using resistive load during startup.

Regards,

jagdish

Hi Jagdish,

Chris is out of office so I will help you answer your question.

This feature of limiting the inrush input current at start up is made to protect the system integrity.
What you see as a load at the output is an average value of the current in the coil. So this device can handle peak current up to 1A before it triggers the current limit when the system is in steady state.

I would recommend you make sure the system is in steady state before applying the load so the current limit will be shifted to a typical 525mA peak to a typical 1A peak. It would then be considering a different power up sequence in your system to have a smoother load start up so the system can start up properly.

If you need more information about your power up sequence, please ask!

Thank you very much.
Best Regards,

Dorian

Hi Dorian,

In my board, 3.4V is powering whole logic section. So you mean I add some logic switch which turns on after some delay till 3.4V becomes stable? This is ridiculous solution which adds unnecessary cost & complexity to the IC.

Regards,

jagdish

Hi Jagdish,

The TPS62175 does not have a Soft Start pin which would allow your system to start up the way you want. I think we need to find another device for your system that has the internal soft start circuitry.

How to use and what type of device is using it is described in the following App Note: slva470a

To help you better, Can you sum up what are the parameters of your system? So we can find the proper fit.

Thank you very much!

Best Regards,

Dorian