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LM5106: About the mean of MDT

masahiko shimizu
Guru 11235 points
Part Number: LM5106

Hi,

I have question about MDT.
I understand MDT is "MDT= |DT1-DT2|" from Figure3.
On the other hand, DT1 and 2 value are tested 510ns at RDT=100kOhm and 86kOhm at RDT=10kOhm under 25 degrees.
Why is MDT defined in datasheet?

Best regards,
Shimizu

  • 0
    TI__Mastermind 20950 points

    Hello Shimizu,

    I am an applications engineer supporting this device, and will work to answer your questions.

    I want to make sure I understand your question correctly. You are asking why is MDT defined in the datasheet?

    In many designs, if you are targeting minimizing the dead time but want to ensure the gate drive will have adequate dead time to turn off one device before the other turns on, you would want to know if there is similar dead times between the two transitions of LO and HO drivers.

    Most half bridge drivers either have propagation delay matching parameters, when there is no dead time feature. Or dead time matching parameters with the dead time feature.

    Confirm if this answers your questions.

  • 0 in reply to Richard Herring
    Guru 11235 points

    Hi Richard,

    Thank you for your reply.

    I can understand about MDT.
    It is the difference of time between DT1 and DT2.
    But I had some question from your answer.

    Q1: DT1 and DT2 are defined as Typ value in datasheet.
    　　Is this value tested at ATE?
    　　Or Is not this value tested?

    Q2: If DT1 and DT2 value are tested at ATE, Does MDT mean the variation by temperature(-40~125) of the difference between DT1 and DT2 ?

    Best regards,
    Shimizu

  • 0 in reply to masahiko shimizu
    TI__Mastermind 20950 points

    Hello Shimizu,

    The values listed in the parameter table are tested at ATE unless there is a note saying it is specified by design. There is no note so this is tested at ATE.

    The variation of dead time with temperature is shown in Figures 15 and 16. The MDT specification in the table is the parameter tested at 25 deg C.

    Regards,

    Richard Herring

  • 0 in reply to Richard Herring
    Guru 11235 points

    Hi Richard,

    Thank you for your reply.

    I understood that TI is tested DT1 and DT2 of datasheet spec(DT1=DT2 -> Same time at 25 degrees).
    But DT1 and DT2 are tested only under case of RDT=100kOhm and RDT=10kOhm.
    I thought that MDT is defined for others RDT resistor case.
    In others RDT resistor case(for example 47Kohm), DT1 is not same DT2.
    At 25 degrees, TI defines the different time of DT1 and DT2 to be under 50ns.
    Is this my idea correct?

    Best regards,
    Shimizu

  • 0 in reply to masahiko shimizu
    TI__Mastermind 20950 points
    Hello Shimizu,
    The DT1 and DT2 dead time Vs resistor value is shown in Figure 19 to illustrate dead time Vs resistor value.
    You are correct that in the table MDT is only specified with the resistor value of 100k Ohms.
    The datasheet does not show MDT for other values of RDT.
    At 25 degrees the DT1 and DT2 difference in time with 100K Ohms is shown as 50ns typical. This is not a maximum spec.

    Best Regards,
    Richard Herring
  • 0 in reply to Richard Herring
    Guru 11235 points

    Hi Richard,

    Thank you for your reply.

    >At 25 degrees the DT1 and DT2 difference in time with 100K Ohms is shown as 50ns typical.
    ->You said that "DT is tested at ATE".
       What kind of test is being done at ATE of DT1 and DT2?
       At 25 degrees, DT1 and DT2 are fixed to 510ns(RDT=100kOhm) and 86ns(RDT=10kOhm).
       Why is the difference between Dt1 and DT2 defined at 25 degrees?
       I think it is contradiction.

    Best regards,
    Shimizu

  • 0 in reply to masahiko shimizu
    TI__Mastermind 20950 points

    Hello Shimizu,

    The ATE test for non automotive parts is at 25 deg C.

    The DT1 and DT2 typical values with 100k Ohms is 510ns, and with 10 k Ohms is 86ns. The time is measured from LO falling to HO rising or HO falling to LO rising as shown in the datasheet.

    MDT is the difference of DT1 and DT2, which is specified with the 100k Ohms RDT. There is not a minimum and maximum specification of DT1, DT2, or MDT in the datasheet.

    The datasheet specifies that min and max limits apply over the temperature range. Unless otherwise specified tj=25 deg C, VDD=12V, HS=0V.

    Best Regards,

    Richard Herring

  • 0 in reply to Richard Herring
    Guru 11235 points
    At 25 degrees, DT1 and DT2 are fixed to 510ns(RDT=100kOhm) and 86ns(RDT=10kOhm).
    But MDT is defined with RDT=100kOhm at 25 degrees.
    Why is the difference between DT1 and DT2 defined at 25 degrees?
    Does TI check DT1 and DT2 to be same time at 25 degrees with RDT=100kOhms at ATE, doesn't it?
  • 0 in reply to masahiko shimizu
    TI__Guru**** 189399 points
    Hi Shimizu-san,

    We do not guarantee the values of DT1 and DT2 with specific resistor values. The values listed in the data sheet are Typical values.
  • 0 in reply to Don Dapkus
    Guru 11235 points

    Hi Don-san,

    Thank you for your support.

    I understand that TI doesn't accurately guarantee this value.
    But I must explain the mean of this listed value in the datasheet to my customer.
    We don't need to guarantee, just want to know the mean of this listed value in the datasheet.

    What is Typical value?
    => Are DT1 value and DT2 value specified by design?
    => Tested at 25 degree but Has TI accepted the some margin of the error of test value?

    Best regards,
    Shimizu

  • 0 in reply to masahiko shimizu
    TI__Guru**** 189399 points
    Hi Shimizu-san,

    As is typically (no pun intended) the case with TI typical values on the d/s, they are measured on a small sample of parts before the part is released to the market. So that is where the values you're seeing on the data sheet came from.

    If this parameter is critical to your customer, then they need to do a system level analysis and determine what they can accept.

    We do not have any further information about this parameter.