BQ25015 issue

Hi Again,

I would really appreciate if someone from TI can back to us. This is holding off our entire project.

Thank you,

Nir.

The datasheet recommends a minimum of

10uF on USB

1uF on BAT

10uF on output of buck

I also suggest grounding AC if not used.

When was the 15 ohm measurement made?  Before or after applying power to the IC?

Thank you Jeff. The 15 ohms (actually it measured from 15 to around 45, depending on which PCBA i test - i have a few prototypes) is there before and after applying the power! Thank you for the note on the caps but i do not think this is the case here - do you?

Nir.

The input capacitor on a buck switching converter is critical to ensure that there is no ringing on at the SW pin the could overvoltage and damage the FETs.  The output capacitor is a bit less critical but still important.  If you measured 15-45 ohms before applying power the first time, then missing capacitors is not the issue.  When measure an uninstalled IC, does it measure the same thing?  If it does, then this may be normal, however unusual, for this IC.  If not, then it is a PCB problem.

Hi Jeff,

Taking this from where it was stopped last week:

I just got a brand new assembled PCB and again, i get a measurment of 24 ohms from the SW pin to ground so the case here is not the missing capacitors you mentioned.

Checking the same path on a bare PCB shows no resistance at all, so it is not a PCB short circuit.

Can this be a bad batch fromTI?

Thank you,

Nir.

Can you remove the IC from the PCB or take an unsoldered IC and measure between SW and GND?  

Hi Jeff,

I just installed new BQ25015 ICs and the problem is gone. I am now measuring about 20Kohm which seems

normal. So, it is only the ICs i had here since if you remember, i checked an unpowered PCBA and the SW to GND was just a few ohms so it was not me doing the damage, it was already there.

Would you like to have a look at them?

Nir.

Can you submit a return through the distributor?

Yes, i will do that.

Thank you for your support, i will implement your notes in any case.

Nir.