LP2985: Dropout Voltage to high

Stefan Habermeier

Part Number: LP2985

Hello,

we are using the LP2985 in a board which we produce now a few years, and everthing was fine.

Now the last boards have problems, and I pinned it down to the LDO.

It seems the last LDOs we used have dropout voltage that is too high.

For testing purpose I assembled the LDO on an extra board and used a resistor to draw current.

(Cin = 4µ7-X5R / Cby = 10nF-X7R / Cout = 2µ2-X7R / LP2985IM5-3V3 / R-load = 47R / load = 70mA)

The old LDO held the output to 3,27V when changing the input voltage from 4V to 3.4V

The new LDO can't hold the output voltage // 4V = 3.15V / 3.8V = 2.99V / 3.6V = 2.82V / 3.4V = 2.65V

I checked the printings on the parts and both have "L0RB", the only difference is the marking on the old one is looking bolder than the marking on the new one.

So I'm not really sure, this is ok for the device, or is there a possibility that i got counterfeid parts?

Thank you

Stefan

over 6 years ago

0 Jason Song over 6 years ago

TI__Mastermind 23361 points

Hi Stefan,

Is it possible for you to post the pictures of the top marking from both devices?

Regards,
Jason Song

0 Stefan Habermeier over 6 years ago in reply to Jason Song

Prodigy 60 points

Hi Jason,

enclosed some pictures. (The dirt around the parts is from the coating we normally use on our boards, i marked all pictures from working parts with a green tick and the ones not working with a red cross) I don't reduce the size of the picture to prevent loss of information.

1) Pictures from an old board with working LP2985

Normal view / Coating removed / backside of part

2) Pictures from a new board with not working LP2985

Normal view / Coating removed / backside of part

3) Pictures from removed not working parts

4) Pictures from parts ordered from RS-Components (I and AI Type / both types are working in our circuit)

I'm not sure, but on the not working parts i found no marking on the bottom side.

Regards

Habermeier Stefan

0 Stefan Habermeier over 6 years ago in reply to Stefan Habermeier

Prodigy 60 points

Hi Jason,

it seems the software don't upload the pictures.

I hope the uploaded PDF will work

/cfs-file/__key/communityserver-discussions-components-files/196/6523.0677.2018_2D00_Jan_2D00_23--Post-with-Pictures.pdf

Regards

Habermeier Stefan

0 Jason Song over 6 years ago in reply to Stefan Habermeier

TI__Mastermind 23361 points

Hi Stefan,

Thanks for the information. Please allow some time for us to investigate the issue. At the same time, do you have the lot trace information that came with the package of the devices you ordered that showed the problems?

Regards,
Jason Song

0 Stefan Habermeier over 6 years ago in reply to Jason Song

Prodigy 60 points

Hi Jason,

At the moment I don't have this information, because we get the complete boards from an ems service provider.

I hope it will be possible to get some additional information, before I contact the ems service provider.

Regards,

Habermeier Stefan

0 Jim Davenport over 6 years ago

TI__Prodigy 330 points

Stefan,

In order for TI to begin the verification process all of the following information is required. Please review the attached customer letter and provide the required information to ti-counterfeit@list.ti.com.

Required information

Completed Counterfeit Request Form.
High quality pictures of the bottom & top of the device(s)
High quality pictures of the 2D bar code labels.
Copies/pictures of shipping documents, i.e. packing slip showing the origin of the devices to TI. (If this information cannot be provided we are unable to provide verification due to uncertainties regarding chain of custody of the products.)
Provide device application.

Once the required information is provided and submitted, your request will be reviewed for verification.

Important Note: The attachment size limit for the group address (ti-counterfeit@list.ti.com) is 1MB. Email lisam@ti.com, and j-davenport@ti.com if your attachments are larger than 1MB.
TI strongly encourages you to purchase all your TI parts either directly from TI or from authorized TI distributors (http://focus.ti.com/docs/general/distribcountryresults.jhtml) and not from the gray market or brokers.

0 Stefan Habermeier over 6 years ago in reply to Jim Davenport

Prodigy 60 points

Hi Jim,

is it possible to get a tendency, with the data I posted?
e.g. low/mid/high chance of counterfeit parts.

We have to contact our ems service provider and some background knowledge will be helpful.

Regards,
Habermeier Stefan