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TPS27S100: Application problems

Zoey Wu
Expert 5855 points
Part Number: TPS27S100

hi expert.

my customer is using tps27s100 and they are having several problems as below. thanks!
1. Will the chip output fault with open drain? they don't need the function and if it is feasible to connect a dummy load.  

2. When the chips works with 2A load at 70 ℃ , will the temp rise be higher than when work under 25 ℃ . They found that the chip's temp will rise to 128℃ with 2A load at 70 ℃ . They are worried about the thermal.

  • 0
    TI__Mastermind 35005 points

    Hello Zoey,

    I am not quite sure what you mean by open drain on the output. Do you mean floating/open load? The device does have open load connection where you can detect if there is a load or not on the output. Refer to section 7.3.4.2 Open-Load Detection in the datasheet.

    For the thermals- it will depend on many factors such as layout and ambient temperature. You can estimate the temperature rise using the following formula:

    In general, at higher temperatures RON will be higher which would lead to a sharper temperature rise. From the datasheet, Rtheta:

    and the RON:

    This assumes a standard JEDEC 2s2p layout... so for 2A at 25C ambient it would translate to approximately a junction temperature of 52C

    Best Regards,
    Tim

  • 0 in reply to Timothy Logan
    TI__Expert 5855 points

    hi tim,

    thanks for your reply!

    my customer doesn't want the open load detection function , but their product with TPS27S100 has already go small production.

    Do u have any advice on this case? thanks!

  • 0 in reply to Zoey Wu
    TI__Mastermind 35005 points

    Zoey,

    If they don't want the open load detection- they can just not put the recommended pull-up from VOUT to VS that would enable open load detection. In this case, the device won't trigger the open load detection (when there is an open load) as there is no current that would conduct into the IN pin.

    Best Regards,
    Tim

  • 0 in reply to Timothy Logan
    TI__Expert 5855 points

    Hi Tim,

    Below is the SCH of my customer.

    They don't add the pull up resistor in their original SCH. Do u have any other advice? thanks~

  • 0 in reply to Zoey Wu
    TI__Mastermind 29480 points

    Hi Zoey,

    The only recommendation I have is to place a blocking diode or ground network if reverse current/polarity protection are needed, please see Section 7.3.4.7 of the data sheet. Other than that, the schematic looks good.

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    TI__Mastermind 29480 points

    Hi Zoey,

    If the customer doesn't want open load detection and is still having issues with it, they can connect a pulldown resistor to VOUT to ensure the voltage stays below the open load threshold. Does this work?

    Thanks,

    Patrick