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TPS5430 can't cold boot in -40C low temperature environment

Tai-Fu
Prodigy 30 points
Other Parts Discussed in Thread: TPS5430

Hi,

I have a big problem !   I use TPS5430 to transfer 12 to 24Vdc input power to 5.0 Vdc output.

Everything is fine when my system operating at 85C high temperature environment in chamber box.

Even wide temperature cycle test from -40C to 85C that our system continue operating.

But TPS5430 can't cold boot up to generate 5.0 Vdc, when I shutdown sytem with turn off power source and waiting 1 ~ 2 hours then turn on the power source (12 to 24Vdc)

The circuit design on ENA pin is floating, and TPS5430 should be start up even if -40C low temperature environment.

Anyone can help me ?

  • 0
    TI__Guru**** 191445 points

    TPS5430 should start at -40 C.  You may have a passive component that has cold temperature issues.   Also I have found that layout is critical for cild start up.  Most important is the location of the input bypass capacitor.  It must be as close as possible to the IC VIN and GND leads.  Does The circuit attempt to start at all?  Can you provide your schematic, layout and some waveforms that show the IC activity (especially the PH node) immediately when Vin is applied?

  • 0 in reply to JohnTucker
    Prodigy 30 points

    Below is schematic and component list.

    L2 = 33 uH, 3.0A

    TC2 = 560 uF, 6.3V

    C139 = 0.01 uF, 0603, 50V

    C11 = 0.01 uF, 0603, 50V

    TC4 = 47 uF, 6.3V, TA cap.

    C3, C4 = reserved.

    This is layout

    Waveform 1  ( room temperature 25C )  Start up when Vin is applied

    CH2 (Blue) = 12Vdc ( Power Adapter Source ) at Pin 7 (VIN)

    CH1 (Yellow) = PH signal at Pin 8

    Waveform 2  ( 25C )

    CH2 (Blue) = 12Vdc at Pin 7 (VIN)

    CH1 (Yellow) = PH signal

    Waveform 3  ( 25C )

    CH2 (Blue) = 5.0 Vdc Output ( net name = 5V_S )

    CH1 (Yellow) = PH signal with 20MHz bandwidth limited.

  • 0 in reply to Tai-Fu
    TI__Guru**** 191445 points

    The 25 C waveforms all look normal.  does it even try to start switching at -40?  First thing I would try is make C11 = 10 uF.

  • 0 in reply to JohnTucker
    Prodigy 30 points

    Actually, this problem was caused by output capacitor. Because the ripple current will increas when temperature is lower than 0C. And TPS5430 has 2A over current limitation.  TPS5430 will not work (boot up) If output capacitor need more ripple current in very low environment temperature (-40C)

    So, the solution is that changing output capacitor.  Good lock.