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Original question:

LP3996: Alternative device and has a Low Iq.

LP3996: Alternate part to LP3996 with the same pinout

Ramana Murthy
Expert 1765 points
Part Number: LP3996
Other Parts Discussed in Thread: LP5996

Dear Sir,

I am using Dual Linear Regulator LP3996.
I am facing an LP3996 failure.
Input is 5V and output also I am getting 5VDC in both channels.
Cab you let me know the reasons for failure?

also requesting you to suggest an alternate part to LP3996 with the same pinout and current capability.

Regards
Murthy

  • 0
    TI__Genius 14245 points

    Hi Murthy,

    The only P2P part that we have like this is LP5996 however it does not have the POR output. 

    The most common causes for damage is abs max violations or reverse current when Vout>Vin+0.3V. So I would recommend doing a spike check using a scope on each of the pins and make sure there are not such issues. 

  • 0 in reply to Kyle Van Renterghem
    Expert 1765 points

    Sir, I need (POR) power on the reset option also.

  • 0 in reply to Ramana Murthy
    TI__Genius 14245 points

    Hi Murthy,

    Unfortunately we don't have any other devices with the same pinout that also have POR feature. 

    Regarding the damaged parts the most common sources of damage are Abs Max violations and ESD which exceeds the ratings of the part. Eliminating those should eliminate the failures since each device is tested before shipping from TI. 

  • 0 in reply to Kyle Van Renterghem
    Expert 1765 points

    Hi Sir,
    Can you suggest TVS Diode or Protection circuit for this IC
    LP3996SD/X-3333/NOPB at input & output?
    I have tested without load, after multiple turns on's it got damaged.

  • 0 in reply to Ramana Murthy
    TI__Genius 14245 points

    Hi Murthy, 

    What does the voltage look like during these tests? We do not specify what components a customer should use, but generally if you select protection components that keep the voltage within the abs max values there shouldn't be any issues. 

    Depending on the type of voltage excursion you are seeing will dictate what sort of protection topology you need.  

  • 0 in reply to Kyle Van Renterghem
    Expert 1765 points

    Dear Sir,

    Sometimes we are getting 3.3V DC and Sometimes 5V DC.
    Continuously we are getting low high signals on POR.
    Can you please suggest, How to resolve this?

    Regards
    Murthy

  • 0 in reply to Ramana Murthy
    TI__Genius 14245 points

    Hi Murthy, 

    As mentioned previously you will need to look at scope shots to determine how you are damaging the LDO. Without scope shots you will be guessing and so would I so I can't provide any further guidance without seeing test data. 

  • 0 in reply to Kyle Van Renterghem
    Expert 1765 points

    Dear Sir,

    Please find the attached scope waveforms of input Voltage and 2 channels output voltages.

    Please note that
    1. I have not noticed any peak voltages at the input.
    2. Output is connected to 220E load in both channels.

    Please find the attached schematic for your reference.

    Please guide me, How to resolve this issue?
    Your earliest reply will be highly appreciated.


    Regards
    Murthy

  • 0 in reply to Ramana Murthy
    TI__Genius 14245 points

    Hi Murthy,

    This shows a DC condition, what about startup, shutdown, and load transients? All those conditions need to be evaluated since those are the cases that most problems in systems cause a spike or exceed abs max or cause reverse current  (Vout>Vin+0.3V). 

    When you say the output is connected to a 220E load, what is that? Is that an electronic load or is it a 220 Ohm resistor to GND? 

    If it is an electronic load then it is critical to make sure the e-load doesn't pull the output voltage negative, e-load pull a set amount of current regardless of the output voltage. So if the load is on before the LDO turns on or after it turns off that could easily damage the LDO.

  • 0 in reply to Kyle Van Renterghem
    Expert 1765 points

    Sir, the Pink waveform is measured on POR in the image attached above, May be because of Internal FET is ON.
    It is staying continuously low.
    But I observed sometimes the internal MOSFET turns OFF, at that time we are getting a proper output voltage of 3.3V DC.

  • 0 in reply to Kyle Van Renterghem
    Expert 1765 points

    Now I am getting output 5V DC, after feeding the Input Volatge:5 VDC.
    Does it work, If I feed 3.3V DC Input?
    If I get the same 3.3V DC at the output. But I need POR should work properly.

  • 0 in reply to Ramana Murthy
    TI__Genius 14245 points

    The device listed on your schematic has both Vout1 and Vout2 set for 3.3V, so the input voltage should be higher than 3.3V to keep the LDO out of dropout. The device will operate for Vin>2V, but it will not meet the EC Table specifications if the LDO is in dropout. 

    However you mention that if you input 5V DC that the output voltages (Vout1 and Vout2) are 5V, this indicates that you have likely damaged the LDO and it will need to be replaced with a new device AND it needs to be protected from damage (abs max violations, reverse current, or ESD events during PCB assembly are the most common sources of damage). 

    Since the LDO seems to have been damaged there is no way to know if the POR circuitry is still intact. It is common for there to be intermittent behavior on damaged devices.