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TPS43060 consumption at power-up (EN pulled to GND)

Simon Tinguely
Prodigy 240 points
Other Parts Discussed in Thread: TPS43060, TPS43060EVM-199

I have a circuit with a TPS43060. Input voltage is 24V, and the TPS43060 outputs 48V.

I noticed a strange behaviour at power-up. We have a preload resistor (550Ohm) that charges input capacitors (total 1980 uF). I measured a much longer time of preload when the TPS43060 is present, altough the EN pin is pulled to the ground. It takes more than 20 seconds, instead of 2-3 seconds.

When the preload is done, the circuit works perfectly.

I got a similar behaviour with the evaluation board TPS43060EVM-199. The evaluation board has around 128uF of capacitor to load. I supply the evaluation board with 24V through a 10k resistor (to have a similar time constant than on my circuit). I put JP1 on OFF position to keep the EN pin to the GND (current should be max 5uA according to the datasheet).

Normally, loading 128uF through a 10k resistor should take around 2-3 seconds to reach 90% of the voltage. Here it takes more than 40s.

It seems that the TPS43060 has a high consumption during start-up, altough its EN pin is low. Is it a normal behaviour? Am I doing something wrong?

  • 0
    TI__Mastermind 35165 points

    Hi Simon,

    This sounds very unusual. The TPS43060 would need to be consuming quite a bit of current to extend the charge time this much and I would not expect it to.

    Is there an external load on the output of the TPS43060 that could be pulling some current in this test set up? Since it is a boost the output will also be charged up to the input voltage even if the TPS43060 is disabled.

    Best Regards,
    Anthony

  • 0 in reply to Anthony F
    Prodigy 240 points

    Hi Anthony,

    Thank you for your reply. There is a only a 330uF capacitor on the output of the TPS43060 (it's included in the 1980uF to load at start-up).

    This unusual consumption appears only when I power-up the circuit. When the voltage stabilize at 24V, the consumption falls down to its specified level. At this point, I short the preload resistor and switch on the TPS43060 by driving the EN pin high. I can measure the expected 48V output voltage.

    I first thought it could come from a design mistake, or a damaged component, but I have the same behavior with the evaluation board. I did not connect any load on the evaluation board output.

    Using a thermal camera, I noticed that the TPS43060 temperature goes up 10 degrees over the ambiant temperature during start-up, and falls down to ambiant temperature when the voltage is stabilized.

    I also measured the MOS gates and the VCC output. VCC and MOS Vgs stay to 0V until I drive EN pin high.

    Best regards,

    Simon

  • 0 in reply to Simon Tinguely
    TI__Mastermind 35165 points

    Hi Simon,

    I checked this out on the EVM with a current limited power supply and do see the same thing. I'm trying to track down where this current is going. So far I have removed the resistors in series with the VIN pin, ISNS+, ISNS- pins and the BOOT to SW capacitor but the high input current is still there. The last connection to break that is to the SW pin and I'll need to check this next week. I might need to cut the trace in order to do this one.

    Best Regards,
    Anthony

  • 0 in reply to Anthony F
    Prodigy 240 points

    Hi Anthony,

    Thanks for checking with the evaluation board. I'm glad that you could reproduce the issue.


    Best regards,
    Simon

  • 0 in reply to Simon Tinguely
    Prodigy 240 points

    Hello,

    Have you been able to do some more tests about this issue? If you have any idea about a workaround or some changes that could reduce this current consumption, that would be very appreciated.

    Thanks and best regards,
    Simon