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TPS63000: High current draw during startup

Mark Cullen
Prodigy 180 points
Part Number: TPS63000

Hi Everyone

I'm using a a TPS63000 to provide a 3.5V supply from a Lithium Ion cell.

The cell voltage may be between 3.0 and 4.2 volts so the device may be working in boost or buck.

I'm finding that the current increases to around 800mA even with no load when I reach about 3.2 volts then suddenly drops to almost nothing when I reach around 3.7 volts.

Any ideas why I'm seeing this rise in current ?

  • 0
    TI__Expert 7925 points

    Hi Mark,

    If I understood correctly, you see continuous high current during startup if the battery voltage is around 3.2 V or lower, but if the battery voltage is 3.7 V or higher, the device starts up properly? If so, you might have to much resistance between the device and the battery or the battery ESR might be too large. During the startup, there will be some inrush current that can create voltage drop on the supply lines or battery ESR. If large enough, this can trigger the UVLO, restarting the device, and so on, the device will oscillate in start-up. 

    Could you please check if your power source is too far away from the device (for example using long wires)? Also, it would be helpful if you could post the schematic, the PCB layout and scope plots (Vin, Vout at least) during the startup?

    Best regards,
    Milos

  • 0 in reply to Milos
    Prodigy 180 points

    Thanks Milos

    I think you may be right

    At the point where I see the problem the device is being driven by another regulator with a 500mA current limit which may not be enough to supply the inrush.