TPS63030: Operating even though EN is low.

Hi Lucas,

it seem like the EN pin is not well connected. do you still observe the issue if re-solder the IC and change it to new one.

Hi Jasper,

Thank you for the help!

I don't have the ability to easily re-solder this IC. I'm guessing this isn't a soldering issue as we are observing this behavior on two separate assemblies and no other IC's (besides the TPS63030) seem to be having this issue.

Thanks!

Lucas

Hi Lucas,

1. could you detail at which condition the issue is triggered? could you measure the waveform of the EN pin, VOUT and L1 and L2 in both normal and abnormal condition?

2. other possible reason is that the IC EN pin got damage during the assemble to test. we can place a RC filter closed the EN pin to avoid ESD or other voltage spike could damage the IC.

3. Did you follow the suggestion in the datasheet to do the PCB layout?

Hi Jasper,

I'll try to grab the waveforms soon and add them here. From previous measurements the inductor sees a switching waveform, VOUT is regulated, and EN is 0V.

I'm doubtful it was damaged during assembly since we have another circuit that uses the same IC and its working fine. Its just this circuit that's having issues. 

Yes, the layout I have is very similar to the suggested layout. 

It looks like I'm maybe not the only one with this issue?

e2e.ti.com/.../680856

Thank you for the help!

Lucas

Lucas,

could you detail how did your bench test to repeat the issue?  what is fail rate (bad units/good units)?

Hi Jasper,

I have an AND gate that ultimately drives the EN pin low. I could induce the issue by tapping the input to this AND gate low repeatedly. It didn't always trigger the issue immediately, but it would normally always occur after a few tries. For context the AND gate sits either high or low, never high-z or open drain. It has plenty of drive strength and it always outputs a low signal when one of the inputs is low.

I only have two units to test with, but both units displayed the same behavior.

Admittedly this isn't a very methodical/repeatable approach to testing, but is the best method I have at my disposal. And even with this approach it was somewhat repeatable and consistent.

Thank You!

Lucas

Hi Lucas,

the AND gate is not related to this issue, I guess. The device just detect the signal at EN pin to determine the operation mode. could you measure the waveform of VIN, EN and VOUT?

Hi Jasper,

Please see pictures below for behavior during normal operation and during an 'event'. 

Thank You!

Lucas

Figure 1: nominal VIN:

Figure 2: nominal EN pin when EN pulled low:

Figure 3: nominal VOUT when EN pulled low:

Figure 4: VIN during issue event:

Figure 5: EN pin during issue event:

Figure 6: VOUT during issue event (aka EN is disabled):

Hi Lucas:

Did you measure the pin near IC directly? And have you measured L1 L2 to check if it's switching. 

I just wonder if adding a pull down resistance can work.

Hi Minqiu,

I've tried measuring both the pins themselves and the connecting vias (about 0.015 inches from the pin), and had the same results.  

I have measured the inductor and found it was switching. 

I could try adding a local pull down. Do you think there could be an issue with the chip not being able to source/sink current during this issue, and adding a pull-down would help with this? 

Thank you for the help!

Lucas

Hi Lucas:

Actually, I only did the test with well pull up or pull down before. And no such issue happened. 

That's why I suggest to add pull down resistance.