LMR14203: Device shutdown above 60C

Hi,

Thank you for providing the schematic and layout for your design. It looks like your design may hit somekind of current limit and shrink the duty cycle.

Here are my comments on your design:

1) Make sure that the 220uH inductor does not go into saturation at your maximum current

2) Check the diode D9, the diode looks quite small and it has to be schottky diode

3) Shorten routing of bootstrap capacitor C20, and use larger traces from SW pin to the inductor

4) Is there anything downstream that may pull more current at higher temperature? Or something that causes the LMR14203 to hit current limit?

5) You may want to put the output capacitor ground closer to the IC. Or at least put a ceramic capacitor from VOUT to GND near the inductor 

You can take a look at this user guide for layout reference

https://www.ti.com/lit/ug/snva502b/snva502b.pdf?ts=1634316108266&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLMR14203

Thank you

-Arief

Hi Arif,

Thank you for your insights. Here is our customer's feedback.

1. The inductor is not 220uH (it was originally, but we reduced it to 68uH) and the pics correspond to 68uH and 68uF (you are looking at the art of the original board, new L & C were kluged in trying to overcome this shutdown issue).  It is a shielded inductor from Coilcraft MSS1048-683ML with a saturation current rating from 1.28A to 1.7A.  The CAP was changed to a 68uFx50V OS-CON type (low esr), but it was too difficult kluging the second in.

2. Diode D9 is a Schottky rated for 40V and 1A, Central Semi CMPSH1-4L

3. I will ensure this is done in rev B of board.

4. The load was a fixed electronic load that we set the maximum on.  The part still shuts down at much lower currents (as low as 20mA).  The in-circuit load is ~160mA MAX and very well-defined (8 0-20mA current mirrors).

5. I will review this in rev B.

Thank you for your help.  Also, very disappointed that we suddenly can’t buy most TI parts, which makes it difficult to design you in (The LM14203X here is NA for > 1 year).

Regards,

Danilo

Hi Danilo, 

Do you know if the part can pull 150mA at room temperature? 

You can also try to put an input ceramic capacitor around 1uF directly at pin 5 and 2 (VIN and GND) and see if that helps

Yes, just like most of the semiconductor industry, supply issue is quite challenging. 

Thank you

-Arief