TPS7A3301RGW regulator reliability

Dave Ngan

Other Parts Discussed in Thread: TPS7A47, TPS7A33

I just want to know if anybody have the same TPS7A3301RGW reliability problem as me.

The circuit is very simple, same as the official datasheet.

Everything is working fine initially until I use my finger to touch the surface mount 1uf NR ceramic cap, the input cap is very near the NR cap, my finger may also touch it the same time. anyway, The circuit stop work immediately, TPS7A3301RGW die.

The second problem is reverse protection. I know the datasheet do not include it, but using a 22uf output ceramic cap and no input cap, the chip also die immediately when power off.

All the above test condition is -20V input and -12V output

The chip are sample from TI directly, is this just a individual batch problem or it's normal?

over 13 years ago

0 Bill Stokes over 12 years ago

TI__Expert 8890 points

Hi Dave,

Does the part begin to work again after the Vin (or EN) is cycled off-on?

The NR node is very high impedance and thus susceptable to noise. The capacitance in your finger may be collapsing the reference voltage but I can't imagine why it would be damaging the part.

I think the data sheet recommends 10uF at the Vin pin. Our experience is that this part does not have problems turning off. If you would like to start the Failure Analysis process it might be good to investigate this problem.

1830.FVF_Dallas.doc

You might try ordering an Evaluation Module (EVM) from the website in order to help verify what you are seeing.

Regards

Bill

0 Dave Ngan over 12 years ago in reply to Bill Stokes

Prodigy 20 points

Hi Bill,

The chip is totally die, I tried Vin (or EN) cycle off-on do not work.

Using a hot air gun replace the chip on the PCB and it work again, but die immediately after I turn off the power.

(The input Aluminum Electrolytic cap is temporary removed due to the use hot air gun)

To compare, I use my finger to touch the nr cap on the tps7a47 only varies the output voltage, the chip will not die.

do you have the tps7a33 evm on hand and touch the NR cap to see if it will die immediately? thanks

0 Bill Stokes over 12 years ago in reply to Dave Ngan

TI__Expert 8890 points

Dave,

I'll be happy to look at this. Please tell me how you are turning off the LDO. Are you using the EN pin, shorting Vin to ground, or simply turning off the upstream supply to the LDO?

Bill

0 Bryan Nevins over 12 years ago

Prodigy 20 points

I had two of them stop working, I could not figure out why. Third one

worked for an extended period.

0 Bhupesh Patil over 12 years ago in reply to Bryan Nevins

Intellectual 440 points

I have used two TPS7A3301 regulators to provide supply for identical circuits on the same board. Layout of both regulators are almost similar. Out of those one regulator get damaged after powering on for some time.

when i checked the resistance between pin1(output) and 2 (nc), it is zero.

what is the reason?

0 Ryan Eslinger over 12 years ago in reply to Bhupesh Patil

TI__Guru 55940 points

Hi Bhupesh,

Since you started a new thread with the same question, I will answer on that thread here:

http://e2e.ti.com/support/power_management/linear_regulators/f/321/p/290365/1012876.aspx#1012876

Very Respectfully,

Ryan

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TPS7A3301RGW regulator reliability