LMR70503: LMR70503 is getting damaged

We are looking into this, and will get back to you soon.

Your schematic looks almost the same as published in the datasheet except for L22. Is L22 a ferrite bead? How do you apply the input voltage? Do you see an overshoot at the VIN pin when you apply the input voltage? If there is an overshoot, it may exceed the IC's maximum rating of 6V and cause some damage. Could you capture VIN to GND waveform when you apply VCC_5V?

Hi ,

Is L22 a ferrite bead?

Yes. It is ferrite Bead

How do you apply the input voltage?

Main input voltage is 24V. We are using 24 to 5V TI regulator TPS5450DDAR.

Do you see an overshoot at the VIN pin when you apply the input voltage?

There is no overshoot at input. Please find below image. 

Thank you for the info.  Two more questions:

1. The waveform seems to be captured by a probe in 50Ohm coupling.  What probe do you use?  Usually we use 1MegOhm dc coupling with a regular voltage probe.

2. Anyway, above voltage waveform is not relevant.  By VIN, I mean the LMR70503 VIN pin.  Can you monitor the voltage of the VIN pin to GND at power up?  I am concerning about the front stage converter's output (TPS5450DDAR?) overshoot that may damage the LMR70503.

Hi

Please find answers below.

1. The waveform seems to be captured by a probe in 50Ohm coupling.  What probe do you use?  Usually we use 1MegOhm dc coupling with a regular voltage probe.

We probed using 1M Ohm Voltage probe.  Please find image which is probed using 1M Ohm probe.

2. Anyway, above voltage waveform is not relevant.  By VIN, I mean the LMR70503 VIN pin.  Can you monitor the voltage of the VIN pin to GND at power up?  I am concerning about the front stage converter's output (TPS5450DDAR?) overshoot that may damage the LMR70503.

Please find image below which is probed at VIN of LMR70503 

Hi Youhao Xi,

Please let us know your inputs on this issue.

The IC can be damaged by an over voltage or over current event. There is a voltage spike before the input voltage rises up. What causes this spike? Could you zoom in this spike and see how high it can go? The LMR70503's VIN max rating is 6V, and exceeding it may cause damage.

Input to the regulator never crossed beyond 5.4V at any time.  

Please let me know over current will damage the IC or not ?

This regulator is used as supply to Op Amps which are working as buffers .

Over current can damage the internal FET but there is a current limit so it will be rare for OC damage. May I bother you to get the switching waveform of SW pin to GND? Please use a very short ground lead--spring tip--for the probe.