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TLV62085: Why the TLV62085 PG Pin will Go to Low when I heat the TLV62085 about 70 degree by hair dryer.

Part Number: TLV62085

The PG pin pull up to the 3.3V_ASIC  by 1M ohm resistor then connector to the other TLV62085's enable pin. When the temp is lower about 70 degree it is work, 

 When The temp higher over 70 degree the PG pin's voltage only has 0.9V.  (3.3*400k/1400k.)  It's 3.3V_ASIC output is still correct 3.3V but PG signal could not push the the next power IC.

I need to reduce the 1M ohm to 10k or 100k that it can work normally.

  • Hello Pingyuan,

    Can you provide the waveform which include the PG and Vout signals at 70 deg.C?

    Best regards,

    Excel

  • Channel 1 (Y):  Vout   .   Channel 2 (B) : PG.  When the pull up resistor is 1M ohm, PG Pin Could not go to High to push the next TLV62085 that the channel 3 power could not wake up.

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    Channel 1 (Y):  Vout   .   Channel 2 (B) : PG.  When the pull up resistor is 10k ohm, PG Pin is work.

  • Hello Pingyuan,

    The PG pin clamps to 0.8V with 1Mohm pull-up resistor (R444) is due to increase on input leakage current (~2.5uA) into PG pin at high temperature. Decreasing the R444 value to 10K will compensate in the drop in PG pin voltage. See figure below for details.

    To calculate for R444 value, determine the minimum high level for PG (PGhigh_min) for the 1.5VDDR to enable. Adding a 20% margin on ILK is highly recommended.

    R444 = (3.3V - PGhigh_min) / ILK

    Best regards,

    Excel

     

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

  • Hi Regidor sir: 

    I could not find the relationship about the temp and leakage current on the SPEC, 

    It describe the average leakage current IPG about 0.01uA and It also use the 1M ohm pull up resistor on the PG pin on the SPEC (Typical Application).

    I have another question about the following figure.

    How to confirm the enable pin is working or the pull down 400k ohm resistor is exit or not.

  • Hello Pingyuan,

    Before I comment to your queries, can you provide the complete circuit focusing on the PW_GOOD? How many unit or sample which has the same issue?

    Best regards,

    Excel

  • Hi Excel sir:

    I have tested 4 pcs MB Board, it 100% will happen in this kind of problem, 1.5V DDR could not enable when I heating the U33 close to the 70 degree celsius . 

    PW Good1 only connect to the U34 enable pin.

     

  • Hello Pingyuan,

    Can you remove R451 then re-check the waveform at 70 deg. C?

    The intention is to isolate PW_GOOD1 to U34 circuit. If PW_GOOD1 is high even at high temp, then it is the EN pin of U34 pulling it LOW at start-up due of the 400kohm pull-down resistor.

    Can share you email address so I can contact you directly?

    Best regards,

    Excel

  • Hello Pingyuan,

    Any update on the requested waveform?

    Best regards,

    Excel

  • Hi Excel sir:

    Sorry for late to reply.  we have Typhoon vacation last weekend in TW. 

    The waveform is ok, when I remove the R451 at 70  deg c.

    [The intention is to isolate PW_GOOD1 to U34 circuit. If PW_GOOD1 is high even at high temp, then it is the EN pin of U34 pulling it LOW at start-up due of the 400kohm pull-down resistor.

    Can share you email address so I can contact you directly?]

    ==> I could not understand why the 400kohm  pull-down resistor won't influence at low temp. If it still there when start up, I think that 1M pull up resistor could not enable the next tlv62085.

    The enable pin voltage will be 3.3*400/1400=0.94V it is lower than 1V. 

    E-mail: Pingyuan_fu@avision.com.tw

  • Hello Pingyuan,

    As mentioned in the e-mail exchange we have. I am closing this thread.

    Thank you very much!

    Best Regards,

    Dorian

  • Hi Dorian :

    About your question in the email 8/19, I think I had replied it again. 

    Could you use two TLV62085 EVM Board to test it?

    I think it is very easy to copy about this issue.

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    For the moment Excel is out of office until 9th of September. I will for the time being help you with your query. I will then close the thread and we will continue here.

    If I come back to your query, Did you remove the R451 and re-check the waveform at 70 deg C?

    Thank you very much!

    Best Regards,

    Dorian

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