LP2985: The design issue for LP2985

Hi Liang,

The Redbull refresh for this device was launched end of 2022, so I don't see any reason that there would be a difference between the lots for these date codes.

I don't see anything wrong with the schematic. Can you share some more information on what is failing? Is it just not turning on? Do you have any waveforms to share to help with troubleshooting? 

Regards,

Nick

Hi Nick,

Thanks for your reply.

We have below testing result:

1. The pin voltage:

2. The log for the testing:

1) The failure device:

2) The good device:

3. BTW, can you advise which the detail waveform or other informaton we need to provide to you for evaluating, thanks?

Nick Butts said:

The Redbull refresh for this device was launched end of 2022, so I don't see any reason that there would be a difference between the lots for these date codes.

Hi Nick,

You say the Redbull refresh for LP2985 was lunched end of the 2022, but our the previous datecode is the 22 week in 2022,

it is on the middle year of the 2022, so I thinks it has some updated the end of 2022? thanks.

Hi Liang,

Thank you for the testing results. How many units were observed to fail in this testing procedure? I see that the device had initially turned on and regulated during Step 1, but then after restarting the supply the device did not turn on. I think it would be good to look at voltage waveforms of the supply restart (Step 4) test. Also, after the foldback test, was the device observed to recover when the short was removed? Maybe they didn't test it since it wasn't part of the testing procedure. 

Zhang Liang said:

You say the Redbull refresh for LP2985 was lunched end of the 2022, but our the previous datecode is the 22 week in 2022,

it is on the middle year of the 2022, so I thinks it has some updated the end of 2022? thanks.

I'm not sure exactly what they mean, but since both of the date codes for the devices that they have are dated before the Redbull refresh was launched they should only have the older silicon so there should be no substantial difference between the lots (besides the normal lot-to-lot variation). 

Regards,

Nick

Hi Nick,

Thanks for your reply.

We consider that the output voltage is Triggered a condition for the pulldown so our output voltage is 0V, all the date code 2421 is abnormal;

Can you help to check when add the pulldown function? and we need to know why LP2985 has no output voltage that we use the same design?

Hi Liang,

The output pulldown is only for the new chip (Redbull), so if they don't have Redbull devices then this isn't a feature on the devices that they have. Can they send a picture of the top marking so I can verify the devices?

Have they collected any of the waveforms I requested? I can't say what the answer is to the issue before I understand it.

Regards,

Nick

Hi Nick,

Nick Butts said:

Thank you for the testing results. How many units were observed to fail in this testing procedure? I see that the device had initially turned on and regulated during Step 1, but then after restarting the supply the device did not turn on. I think it would be good to look at voltage waveforms of the supply restart (Step 4) test. Also, after the foldback test, was the device observed to recover when the short was removed? Maybe they didn't test it since it wasn't part of the testing procedure. 

1. The DC2421 chips are not able to recover the output voltage when the short was removed, the failure rate is 100%. the DC2222 chips are able to       

     recover the output voltage when the short was removed;

Nick Butts said:

The output pulldown is only for the new chip (Redbull), so if they don't have Redbull devices then this isn't a feature on the devices that they have. Can they send a picture of the top marking so I can verify the devices?

2. Plese refer to the picture and waveform:

    The date code 2421 picture:

The date code 2222 picture:

3. The waveform；

Short circuit the P7 and turn on for 2222 date code:

Short circuit the P7 and turn on for 2421 date code:

Hi Liang,

Can they capture waveforms that also include the input voltage? 

Do the devices recover after power cycling the input? Or do they appear to be damaged? You said the failure rate is 100%; how many devices have failed?

Thanks,

Nick

Hi Nick,

We have no idea to judge if this device is damaged or not, but our current test results is the new date code(2421) has no output in the same design;

This is the mass product, our production line SMT more than 100 boards and all the device( date code 2421) are faiure;

and we consider if LP2985-33DBVR has some PCN updated between 2022 and 2024;

Or if we need to submit the FAR to TI CQE?

Hi Liang,

If the board is power cycled does the device regulate until the short-to-ground event? That would be at least some indication of whether the device is damaged.

I looked back at the date codes and if I'm not mistaken the date codes are actually June 2022 and May 2024. Is that correct? They mentioned before that the date code that I think is May 2024 is 2021 instead. If I'm correct then yes there is a PCN between these date codes because the 2024 devices are almost certainly the Redbull devices.

I looked through the final validation review as well as the design verification report for the Redbull project and I see no indication of the device not being able to recover after a short-to-ground event. Since there is simulation data and bench data showing the device recovering from the short, I suspect that there is something else going on that is preventing the device from starting back up. 

The waveforms that they showed have almost no information on them (V/div and s/div), and only include the output voltage. If they want to submit an FA request, they will need to collect higher-quality data for that. So, please ask them to take more waveforms showing both the input voltage and output voltage, and include the full screen so that we can see the scales for the voltage and time. Is it possible for them to measure the input current? If they can cut the input trace and solder a wire and measure the current into the device during the short event, that would be very illuminating.

Regards,

Nick

Hi Nick,

Nick Butts said:

I looked back at the date codes and if I'm not mistaken the date codes are actually June 2022 and May 2024. Is that correct? They mentioned before that the date code that I think is May 2024 is 2021 instead. If I'm correct then yes there is a PCN between these date codes because the 2024 devices are almost certainly the Redbull devices.

Plesae kindly provide the PCN to our end customer for evaluating, thanks.

Hi Liang,

Sent the PCN through email. 

Regards,

Nick

Hi Nick,

Thanks for your support, I have got the PCN.

We consider the "Output Pulldown" is the main issues for our design bucause we use the Vout status(3.3V_GPS) to control the ON/OFF pin,

so the "Output Pulldown" funciton will set the low if there are no output voltage, we need to modify our design or softwave to solve this problem;

Now we have below issue that please help to comfirm:

1. Pleaes advise if both the New chip/ Legacy chip add the "Output Pulldown" function, or only the New chip add the "Output Pulldown" function?

2. If now the new chip add the "Output Pulldown" function, how to distinguish between New and Legacy chips? Can we get the detail information from the 

   top surface silk screen printing?

3. The "Device Nomenclature" is write: "M3 is a suffix designator for newer chip redesigns, fabricated on the latest TI process technology“,

    so I think we can read the chip top surface silk screen printing by the "M3" character? it is right?

4. The finally, it is most important, we are afraid TI will send us the mix up the goods that Internal Integrate the "Output Pulldown" function and

non-Internal Integrate the "Output Pulldown" function, there are significant challenges to production because we have no idea the provide the 

standard production process to our factory;

5.It is very urgent to write for your support becuase we will be line down if there are no soluton to solve this issue, thanks.

Hi Liang,

I am collecting this information. I will get back to you first thing Monday. 

Regards,

Nick

Hi Nick,

Thanks, please kindly check if there are any updated, we need to reply to customer today, thanks.

Hi Liang,

I'm still waiting for more information on the output pulldown circuit and the top marking, but I have details to share for the other questions. 

Zhang Liang said:

The "Device Nomenclature" is write: "M3 is a suffix designator for newer chip redesigns, fabricated on the latest TI process technology“,

    so I think we can read the chip top surface silk screen printing by the "M3" character? it is right?

The new devices will not have "M3" on the top marking. The new devices have "LPFG" on the top marking, while the old devices have "LPFL". Do they see this on the devices they have?

Zhang Liang said:

4. The finally, it is most important, we are afraid TI will send us the mix up the goods that Internal Integrate the "Output Pulldown" function and

non-Internal Integrate the "Output Pulldown" function, there are significant challenges to production because we have no idea the provide the 

standard production process to our factory;

Yes I understand your concern. The best solution to this is to change the part number to the orderable part number LP2985-33DVBRM3 because this is the orderable number for the new device and so they will certainly not receive legacy devices with this part number. This is the same device with same behavior as the new device that is phasing out the LP2985-33DBVR. The alternative is to attempt to work with our planning team and the sales representative for this customer (if there is an assigned one) to get them supply of new devices.

I'll update you when I have answers to the other remaining questions. I'm expecting to hear back tomorrow. 

Regards,

Nick

Hi, Nick,

Nick Butts said:

The new devices will not have "M3" on the top marking. The new devices have "LPFG" on the top marking, while the old devices have "LPFL". Do they see this on the devices they have?

No, both of the 2222+5 and 2421+5 goods are the "LPFG" marketing, and baed on your screenshot, the Marketing of the old device are

both "LPFL" and "LPFG", is it right?

Nick Butts said:

Yes I understand your concern. The best solution to this is to change the part number to the orderable part number LP2985-33DVBRM3 because this is the orderable number for the new device and so they will certainly not receive legacy devices with this part number. This is the same device with same behavior as the new device that is phasing out the LP2985-33DBVR. The alternative is to attempt to work with our planning team and the sales representative for this customer (if there is an assigned one) to get them supply of new devices.

Yes, thanks for your kindly suggestion, but your know, we have ordered the 2222+5 and 2421+5 two lots device, and we only need to know the 2222+5

has "output pulldown" function or not, and how to distinguish the old and new device, we have no idea because the datasheet has no information to 

explain this issue;

Nick Butts said:

I'll update you when I have answers to the other remaining questions. I'm expecting to hear back tomorrow. 

Sorry for my reply is delay because of the  "Chinese National Day" , and we still wait for your suggestion, thanks.

Hi Liang,

Zhang Liang said:

No, both of the 2222+5 and 2421+5 goods are the "LPFG" marketing, and baed on your screenshot, the Marketing of the old device are

both "LPFL" and "LPFG", is it right?

I've looked through our system and I am not seeing at which A/T site the top marking would be "LPFL". It may be a typo in the datasheet - I need to confirm. 

Zhang Liang said:

Yes, thanks for your kindly suggestion, but your know, we have ordered the 2222+5 and 2421+5 two lots device, and we only need to know the 2222+5

has "output pulldown" function or not, and how to distinguish the old and new device, we have no idea because the datasheet has no information to 

explain this issue;

I have confirmed that the old device does not have a pulldown circuit on the output and the new device does have it. If they still have the shipping labels, the CSO (chip source origin) RFB indicates a new device from RFAB and CSO anything else indicates an old device. 

Regards,

Nick

Hi Nick,

Nick Butts said:

I've looked through our system and I am not seeing at which A/T site the top marking would be "LPFL". It may be a typo in the datasheet - I need to confirm

Thanks, we wait for your information;

Nick Butts said:

I have confirmed that the old device does not have a pulldown circuit on the output and the new device does have it. If they still have the shipping labels, the CSO (chip source origin) RFB indicates a new device from RFAB and CSO anything else indicates an old device. 

Thanks, please advise how to get the information of CSO and RFB, it is in the shipping labels? We will check if the factory still retain this labels.

Hi Liang,

I found that there is still an active A/T site that uses "LPFL" for the top marking and there are other A/T sites that are still active that use "LPFG" as well, so it's not a typo in the datasheet.

The "CSO" is on the shipping label; it will look like this "CSO: RFB". Another way we can work to verify the chip origin is to use the lot trace code "LTC" on the shipping label. If they don't have the shipping label anymore it will be a lot more difficult to trace where they came from. 

Regards,

Nick

Hi Nick,

Got it, this is useful for our factory, and I communicate with them firstly and feedback to you soon.

Hi Nick,

Our 2421+5 goods lot# is 4209161CDA, and there is the CSO:RFB, it maybe the new chip;

Hi Liang,

Devices with CSO:RFB are definitely Redbull devices. If it's anything other than RFB, it's the legacy chip.

Regards,

Nick

Hi Nick,

Our factory feedback it is difficult to separate the CSO:RFB and other on the shipping label, so please help to confirm below:

1. We need to release the order based on the part#LP2985-33DBVR, and it is all the new chip production process(include output pulldown function), right?

    TI will not send the Legacy chip after the PCN?

2. Our 2024 datecode goods is the part# LP2985-33DBVR but not the LP2985-33DBVRM3, but the 2024 datecode goods is new chip, it is different 

    interpretation in the datasheet?

3. Above all, we need to know how to solve this issue if we need the consistency chip production process, and must we to updated our order

    part# from LP2985-33DBVR to LP2985-33DBVRM3? thanks.

Hi Liang,

We can only guarantee that the devices will only be new devices if we were to work with a planner to route them specific materials, or if they changed to the M3 part number. My understanding is that to work with the planning team this would need to be an assigned account. Is there an assigned TI employee for your company? 

The PCN date does not indicate that legacy devices will not be shipped going forward. The legacy devices will still ship until the supply of them is gone, and then only new devices are shipped. To my knowledge this is how the refreshed devices are being handled company wide. 

Zhang Liang said:

2. Our 2024 datecode goods is the part# LP2985-33DBVR but not the LP2985-33DBVRM3, but the 2024 datecode goods is new chip, it is different 

    interpretation in the datasheet?

Yes I think the nomenclature table could be more clear because the non-M3 device can be either the legacy device or the refreshed device. The M3 device will always be the refreshed device. 

Zhang Liang said:

3. Above all, we need to know how to solve this issue if we need the consistency chip production process, and must we to updated our order

    part# from LP2985-33DBVR to LP2985-33DBVRM3? thanks.

The cleanest solution is to switch the part number to the M3 device. If this isn't possible on your end then the alternative is to see what we can do about working with the planning team to get you only new devices. 

Regards,

Nick

Hi, Nick,

It is very difficult to modify the part# to -M3 suffix because the factory has about 20+ parts# based on the LP2985;

Nick Butts said:

The PCN date does not indicate that legacy devices will not be shipped going forward. The legacy devices will still ship until the supply of them is gone, and then only new devices are shipped. To my knowledge this is how the refreshed devices are being handled company wide. 

We need to communicate with our end customer for the TI's updated, but we have no PCN or datasheet to explain this functional confusion problem,

can you help to push the progress to update the PCN or datasheet that we can get the information that the part# LP2985-33DBVR are include

the legacy devices and new devices design? thanks.

Hi Nick,

Please kindly review above issue, and our end customer need us to provide the solution because the factory CQE consider it is the risk for the production line, thanks.

Hi Liang,

I apologize for the lapse in support. I have reached out to our planning team, but the planner for this device is out of office today so I will have to wait until tomorrow to see what we can do about this.

Regards,

Nick

Hi Nick,

Please kindly check if there are any future solution for this issue, thanks.

Hi Liang,

Sorry for the delay. I'm discussing with the planning team to see what we can do. 

Do you know what kind of solution would work for them in the near-term? If we were to ship them enough supply to get through x number of months for now, would that work for them for now? The real issue is that it's very difficult to know how long it will take to go through the supply of old devices, so projecting a time frame to fill their supply needs until the old devices are gone is difficult. 

Regards,

Nick