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TPS54327 unexpected simulation results in TINA

Vitor Soares
Prodigy 40 points
Other Parts Discussed in Thread: TPS54327

Hello.

I am simulating the component with TINA, but the results are completely unexpected regarding the specs in datasheet.

VIN is 12V, and the pretended output to 3.3V.

Recommended circuit in datasheet: http://www.ti.com/lit/ds/symlink/tps54327.pdf

Recommended values in same datasheet: 

Circuit implementation in TINA:

Output of transient analysis Vout = 1,33V.

What is wrong here? The output voltage is nothing to do with 3.3 V. Should I trust this simulation?

 Really appreciate your help,

Thank you in advance.

  • 0
    TI__Guru**** 191445 points

    Try changing the load resistor.  3.3 V into 350mohm is 9.43A.

  • 0 in reply to JohnTucker
    Prodigy 40 points

    Hello John,

    Thank you for your help. You were right. The output voltage is the right place. Any way, I still have some issues in the same simulation that you might help me again.

    With a 18nF capacitor in SS pin, I am expecting a start up delay of aprox 7.5 ms. The Vout in simulation just takes 2.2 ms. 

    Can you see anything?

    Thank you,

    Vitor

  • 0 in reply to Vitor Soares
    Prodigy 40 points

    Hello again. Sorry to keep asking, but i need your feedback about this simulations/validations. 

    To make that approx 7.5 ms delay in Vo rise, I need to use a 62nF capacitor rather 18nF. 

    Is this a valid simulation of the component behaviour?

    Many thanks,

    Vitor

  • 0 in reply to Vitor Soares
    TI__Guru**** 191445 points

    I will have to check it.

  • 0 in reply to JohnTucker
    TI__Guru**** 191445 points

    From the TINA model schematic notes:

    TEST BENCH DESCRIPTION:
    1. The TPS54327 Transient Model is encrypted.
    2. The testbench has been configured for VIN= 12V VOUT= 1.05V, Iout = 3A
    3. This application has been corner tested for input voltage ranges: 4.5V to 18V and Iout: 0A to 3A.
    4. MODE is a parameter used for FAST SoftStart. Set MODE = 1 for fast startup time ( 6x speed of normal softstart) to enter steady state faster.
        Default is MODE=0 used for normal softstart based on Css.
    5. Operating current and shutdown current have not been modeled.
    6. Thermal characteristics of the part have not been modeled.

    You are operating in MODE = 1 so your slow start times are artificially fast.