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LMH0384: What is the Theta(junct-to-board) for this part

S West
Prodigy 20 points
Part Number: LMH0384

What is the Theta(junct-to-board) for the LMH0384. Data sheet only gives Theta(JA) and Theta(JCtop)

Thanks!

  • 0
    TI__Guru* 93400 points
    Greeting West,

    Theta JB is about 40DegC/W.

    Regards,,nasser
  • 0 in reply to Nasser Mohammadi
    Prodigy 20 points

    Hello Nasser, I believe the 40 Deg C/W value you mentioned is the Theta JA (Junction to AMBIENT) and not Junction to BOARD.

    The Theta(JB) is always significantly lower than the Theta(JA).

    Do you happen to know the Theta(JB)?

    Thanks,

    Sid

  • 0 in reply to S West
    TI__Guru* 93400 points
    Hi Sid,

    40Deg/W is based using the following equation:
    Tj=T(pcb) + (ThetaJBXPower).
    Tj= Junction Temperature = 101 Deg C
    T(pcb) = 85 Deg C
    LMH0384 Power = 3.3 X .120.
    Then I back calculated Theta JB. This parameter is board/layout dependent and it has not been characterized so I back calculated this. You can change your T(Pcb) and power to determine your Theta JB.

    Regards,,nasser
    I used maximum power consumption(120mA at 3.3V) and used Maximum junction teemperature