LV284: LV2842 experienced a malfunction where some chips had no output during mass production

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Part Number: LV284

Tool/software:

（1）LV2842XLVDDCR

（2）The schematic diagram and PCB diagram are as follows：

（3）The failure rate is about 1%, and most of them can start normally after being powered on again, while a small portion still cannot start after being powered on again.
Application Description: Vin=4.8V, Vout=3.3V, Iout=50-300mA.
Power on process: Vin is powered on first, and after about 200ms, the chip output is enabled.
When the faulty chip is enabled, the chip's SW has no output. After a few hundred milliseconds, the SW has output, but all of it is attenuated oscillation waves.
After the faulty chip is heated, it can return to normal, but it may not output again after being left for a period of time.

Please assist in the analysis, thank you！

10 months ago

0 Rahil Ajani 10 months ago

TI__Genius 9460 points

Hi,

I will look into this and back you you.

Regards,

Rahil

0 Rahil Ajani 10 months ago in reply to Rahil Ajani

TI__Genius 9460 points

Hi,

Where is unit 19 on the layout?

Regards,

Rahil

0 ?? ? 10 months ago in reply to Rahil Ajani

Prodigy 20 points

0 ?? ? 10 months ago in reply to ?? ?

Prodigy 20 points

This is the SW waveform during abnormal conditions

0 Rahil Ajani 10 months ago in reply to ?? ?

TI__Genius 9460 points

Hi,

It's a bit difficult to trace the layout, could you send me your files or a picture without the GND polygon?

Additionally could you please send scope shots of Vin, Vout, SW and Inductor current?

Regards,

Rahil

0 ?? ? 10 months ago in reply to Rahil Ajani

Prodigy 20 points

Hi，

This is a normal waveform，Yellow is Vin、Purple is EN、Blue is CB、Green is SW，When vcb=2V, the chip starts normally.

This is a abnormal waveform，Yellow is Vin、Purple is EN、Blue is CB、Green is SW，When vcb=0.8V, the chip starts abnormally.

The above experiment was conducted on the same printed circuit board and same chip, with the only difference being the VCB. One was 2V and the other was 0.8V. When VCB=0.8V, the chip startup would fail, while the startup of other chips is not related to VCB.

Can we determine if this has been damaged.