TPS7A39: TPS7A39

user6189521

Part Number: TPS7A39
Other Parts Discussed in Thread: OPA2210,

Dear SME, my circuit input is +-12V, the output is +-5v used for powering amplifier OPA2210. +-12V go through 1amp fuse and supplied to TPS7A3901.

however, when I powered on +-12V, the 12V voltage after the fuse go to only about 2.1V, the -12V voltage after fuse go to about 11V. The power is about +-12V.

And I measured the resistor of the fuse, it seems Ok. But there is large volate drop on the fuse.

Do you anyone have any idea about this issue, this is the first time I use TPS7A39. I have no idea what's wrong with it. I checked the circuit and It's really confusing.

Is there any short circuit?

Appreciate for the response.

thank you.

David

over 4 years ago

0 JCHK over 4 years ago

TI__Mastermind 44620 points

HI David,

Can you send a scope shot of what you are seeing and if possible the schematic? normally a fuse has a very low effective resistance. If the input voltage is dropping when you enable the TPS7A39, what is the source impedance of the 12V rail?

0 user6189521 over 4 years ago in reply to JCHK

Prodigy 60 points

Hi JCHK

Thank you for the quick feedback. The following is my schematic, and I marked the voltage measured by multimeter. Thank you

Best regards

David

0 JCHK over 4 years ago in reply to user6189521

TI__Mastermind 44620 points

Hi David,

The image did not come through.

Can you try to upload it again?

0 user6189521 over 4 years ago in reply to JCHK

Prodigy 60 points

Hi, JHCK

Sorry, I re-post the pictrtue again. Thank you.

David

0 user6189521 over 4 years ago in reply to JCHK

Prodigy 60 points

Hi, JCHK

As supplementary iformation, TPS7A39 become quite hot after powering on.

Regards

David

0 user6189521 over 4 years ago in reply to JCHK

Prodigy 60 points

Hi, JCHK

Thank for your help.

TSP7A39 provide +-5V power to OPA2210. After I remove OPA2210 from the PCBA, +-5V is generated perfectly.

It's werid, what's wrong with the OPA2210. Do you have any idea. Below is the diagram.

Thank you again

David

0 user6189521 over 4 years ago in reply to JCHK

Prodigy 60 points

the picture is not displayed, i post it again.

0 JCHK over 4 years ago in reply to user6189521

TI__Mastermind 44620 points

Hi David,

I would have to ask someone from the Op-amp team to see what is going on. At first glance, each op-amp uses the worst-case current of up to 3.25mA. So worst case U3A and U3B are only drawing 6.5mA. This is not likely the issue.

If the +/-12V rail comes up together, the TPS7A39's startup tracking feature ensures that the +/-5V rail would come up together. How is this sequencing look in relation to the -15V rail D2? If the OPA2210 requires that both the +/- rail come up together and the +/-12V rail do not, one simple trick is to add an RC on the input from +12V to the enable pin of the TPS7A39. This might give time for the -12V rail to come up first before enabling the TPS7A39.

I have notified the Op-amp team to see if there are any sequencing concerns.

Power management

Power management forum

TPS7A39: TPS7A39