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LDO for Vin(max)=10V~15V，Vout=3.3V，Io(max)=0.3~0.5A，SMD package，operating temp：-40~125℃

Arthur Huang
Expert 6065 points
Other Parts Discussed in Thread: LP2989, TPS62170

Hi Team,

my customer is looking for the LDO for below operation condition, do you have any suggestion for this application?

Vin(max)=10V~15V，Vout=3.3V，Io(max)=0.3~0.5A，SMD package，operating temp：-40~125℃

On the other hand, do you think if the LP2989 suitable or not for the above operation condition?

For the LP2989, how many power consumption on the condition of (Vi=8.5V, Vo=3.3V, Io=0.2A) and what’s the relation of temperature when rise? what's the  min/max/typ of the Iq value? Do you have EVM board to test?

 

Thank you.

 

Regards,

Arthur

  • 0
    TI__Guru*** 148910 points
    I'm not an LDO engineer, but I think you need a SMPS in order to reduce the power dissipation of your system to reasonable levels. The TPS62170 is a small device which can do what you need.

    (The power dissipation of any LDO is ~= (Vin - Vout) * Iout.)
  • 0
    TI__Mastermind 22610 points
    What Chris said is 100% true, for the described conditions the power dissipation in the LDO will quickly push the junction temperature to thermal shutdown.

    The WEBENCH® Designer tool at www.ti.com can quickly sort through TI power devices to find appropriate solutions.

    For your LP2989 questions:
    1) No, LP2989 is not suitable for the listed operating condition (i.e. Vin= 10V to 15V, Vout= 3.3V, Iout= 300mA to 500mA). The best case (lowest) power dissipation would be ((10V-3.3V) x 0.3A) = 2.01W. The worst case (highest) power dissipation would be ((15V-3.3V) x 0.5A) = 5.85W. Note that 'SMD package' is generic term (i.e. surface-mount device), all three LP2989 packages (WSON/NGN, SOIC/D, and VSSOP/DGK) are considered 'SMD'. Only one package (WSON/NGN) will be anywhere near to providing the needed thermal performance.
    2) For Vin=8.5V, Vout=3.3V, and Iout= 0.2A, the power dissipation (Pd) is ((8.5V-3.3V) x 0.2A) = 1.04W.
    3) The relationship of temperature rise to power dissipation is defined by Rθja.
    Trise= (Rθja x Pd)
    Tjunction = (Tambinet + Trise)
    4) The LP2989 datasheet parametric 'Ignd' is the equivalent of 'Iq'. The datasheet Electrical Characteristics table has typical values and max limits for Ignd. Additionally, the Typical Characteristic section has assorted curves for Ignd.
    5) There is no EVM board available for LP2989.