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TPS61010: Boost converter slow startup issues on new design

Jeff Lynam
Prodigy 190 points
Part Number: TPS61010
Other Parts Discussed in Thread: TPS61220, TPS61021A

Hello,

I have a new board design the is using a TPS61010 to convert a 1-cell AA to 2.3V.  I have experienced several power-up issues with the microcontroller in the design and now believe it is related to the slow-start of the TPS61010.  There is only about 10mA normal load from the basic circuitry.  I have noticed that from a log-idle, cold startup the unit will draw an additional 60-80mA.  I have narrowed the added draw down to the TPS61010.  If after several minutes I perform a rapid power-off/power-up cycle it comes back to 10mA.  The power-up waveform has a rapid on transition, approx 500µs, to 1.2V, then a 500ms transistion from 1.2V to 1.25V, then another slow arc-shaped transition over 3 seconds to go from 1.25V to 2.3V.  Any thoughts on what may be the likely cause of this and what can be done to correct?

Thanks

JR

  • 0
    TI__Mastermind 46905 points

    Hi Jeff,

    from the input output condition. the TPS61220 should be better solution than TPS61010 if there is opportunity to change the IC.

    about the observation of TPS61010, could you share waveform of VIN and VOUT for demonstrate it? i'm not clear about the issue from your description.

    also please share the schematic and layout.

  • 0 in reply to Jasper Li
    Prodigy 190 points

    Hey Jasper,

    Thanks for the response.  Upon initial comparison of both datasheets, the TPS61010 is a little underated for max current in our application, but has worked, and it looks as though the TPS61220 is even lower.  Not looking like a good fit given our 400mA-650mA surge startup loads.  Wave form of Vout below.  Vin is virtually unchanged during the startup cycle.  Schematic and layout are nearly identical to datasheet.  I have noticed that the convertor startup is somewhat sensitive to residual LOW voltages as it transitions to HIGH on the ENABLE input. Please advise.  Thanks

    Jeff

  • 0 in reply to Jeff Lynam
    Prodigy 190 points

    Waveform attached here ...

  • 0 in reply to Jeff Lynam
    TI__Mastermind 46905 points

    Hi Jeff,

    could you measure the input voltage at the same time?

    from the waveform, the VOUT reaches the 2.2V in short time, which doesn't match your description in the first post.

    what is the required output current in this application?

  • 0 in reply to Jasper Li
    Prodigy 190 points

    Hey Jasper,

    Capture of Vin and Vout, at this stage, would require teardown of current I2C bus problem debugging and re-setup.  I assure you, the Vin is 99% flat when POWER-ON of the TPS61010 occurs.  There is a tiny fluctuation of 3-4mV for less than 10µs on Vin.  This tiny blip is imperceptible on the 400ms HORIZ sampling scale needed for the measurement to capture the long startup in the waveform.

    The waveform is nearly exactly what I described.  You will notice that the VERT scale is 1V/div and the HORIZ is 400ms.  Actual 2.2V is not reached until after the 7th division from the sharp trigger transition.  That would make it 2800mS+ to the actual 2.2V.  That is not a short startup time.

    As I mentioned in a previous post, our application needs are 400mA-650mA surge current at startup loads for approx. 1-4 ms. 

    Thanks

    -Jeff

  • 0 in reply to Jeff Lynam
    TI__Mastermind 46905 points

    Jeff,

    thanks for the detail explanation. I understand the issue.

    1. i'm thinking if the issue is caused by the large output current during device startup. from Figure 15 in the datasheet, the current limit is small at low output voltage condition. to confirm this root cause, could you disable the loading during the device startup to confirm the root cause?

    2. this device can't support 400~650mA output current.  such high output current means at least 1.2A switching current of the converter. So I would suggest TPS61021A. However, please note that the output current capacitor of a boost  is normally not stronger during startup. please apply an EVM to evaluate firstly.