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LP2985-N: Vout vs temp and temp drift

Given Ding
Expert 7405 points
Part Number: LP2985-N

Hi Team,

Here is a question from customer. 

Customer use LP2985-3.3V as Vref for high accurate ADC and they find Vout changes with temp and different part changes at different amplitude. So customer hope to get help on below: 

1. Vout vs temp curve.

Customer want to know how Vout changes with temp( -40~125C  Tj). I see datasheet that fig 2 shows 3.3V version part curve but at a specified condition. So for different load, is the amplitude of variation same? since customer's application is different from fig 2 and customer hope to get the curve at their condition, so which parameters mainly affect the curve? 

2. customer find different part has different variation when temp changes.  Considering the difference of parts, please kindly provide a max value of amplitude of variation when temp is -40 to 125C Tj.  

If any question, please let me know.

Thanks.

BRs

Given

  • 0
    TI__Expert 7405 points

    Hi Team，

    Regarding #1，In addition，customer application is 4.5Vin and 70mA load. Thanks.

    BRs

    Given

  • 0 in reply to Given Ding
    TI__Mastermind 23361 points

    Hi Given, 

    1. Vout vs temp curve.

    Customer want to know how Vout changes with temp( -40~125C  Tj). I see datasheet that fig 2 shows 3.3V version part curve but at a specified condition. So for different load, is the amplitude of variation same? since customer's application is different from fig 2 and customer hope to get the curve at their condition, so which parameters mainly affect the curve? 

    --Figure 1 in the datasheet is meant to provide a typical Vout shifting across temperature at the given conditions. When customers are looking for the output voltage tolerance, I would suggest them to design with 6.5 Electrical Characteristics table instead of the performance of a group of units with very limited numbers, please see "output voltage tolerance" table as the followings:

    2. customer find different part has different variation when temp changes.  Considering the difference of parts, please kindly provide a max value of amplitude of variation when temp is -40 to 125C Tj.  

    --This question can also be answered using the table I pasted for question 1. The output voltage tolerance is mainly decided by the tolerance of the internal voltage reference. 

    Regards, 
    Jason Song

  • 0 in reply to Jason Song
    TI__Expert 7405 points

    Hi Jason,

    Thanks for your reply.

    Per customer request, they think total +/-3.5% is large in their application, so  they hope to get tolerance on below condition:

    1. IL=50mA, Tj=-40 to 150C

    2. IL=70mA, Tj=-40 to 150C

    customer can make the load current fixed at one point and just change the temp, so they hope to see if tolerance can be smaller at this condition.

    Thanks.

    BRs

    Given

  • 0 in reply to Given Ding
    TI__Mastermind 23361 points

    Hi Given, 

    The 3.5% limit is coming from the production test, and we are unable to provide min and max tolerance at a particular application condition without having new tests added to the final test program. 

    What's the tolerance they are looking for? Do you think they are willing to run their own validation and using statistic methods to find tighter limit if they need to?

    Regards, 
    Jason Song

  • 0 in reply to Jason Song
    TI__Mastermind 23361 points

    Hi Given, 

    I am closing the thread here as it has been moved to support via emails. 

    Regards, 

    Jason Song