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SN6505B: what's the Absolute Maximum Ratings Peak output switch current @ 90 degree C?

Max Han
Intellectual 2260 points
Part Number: SN6505B

Hi 

in SN6505B datasheet, the Absolute Maximum Ratings Peak output switch current @ 25 degree C is 2.4A.

Recommended Operating Conditions Output switch current - Primary side is 1A.

now customer's application input is 5V, they can see 1.2A peak inrush current at SN6505B startup, and in some projects, the output capacitor is even larger, so the peak current will be 1.8A. inrush current waveform is as below.

customer want to know what's the Absolute Maximum Ratings Peak output switch current @ 90 degree C of SN6505B?

can 1.8A inrush current be support by SN6505B at 90 degree C?

  • 0
    TI__Guru 55815 points
    Hi Max,

    All the values listed as typical (and not as min or max) in datasheet are the values measured at TA = 25C. 2.4A of peak output switch current specified in absolute maximum ratings of SN6505x datasheet is the maximum (and not typical) the device can support across temperature. Hence this current spec is valid for upto TA = 125C.

    Please note that the absolute maximum ratings provided in datasheet are not be operated at regularly and are only meant as limits for undesired fault conditions. Inrush current is going to happen every time there is system power-up and is considered to be part of regular device operation. Hence the recommended current limit spec of 1A from datasheet would be applicable even for inrush current.

    Considering that the 1.8A of inrush current is only happening for about 10ms, it may not affect device's lifetime but since this is exceeding recommended operating conditions we would not be able to guarantee device's lifetime under such operation.

    Let me know if you have any other questions, thanks.


    Regards,
    Koteshwar Rao
  • 0 in reply to Koteshwar Rao
    TI__Intellectual 2260 points

    Hi Rao,

    becuase SN6505B has a fixed soft start, if customer needs to reduce inrush current to below 1A, how does customer do?

    thanks.

  • 0 in reply to Max Han
    TI__Guru 55815 points
    Hi Max,

    I understand your concern. With the suggested decoupling capacitors, we do not expect to see much of inrush current.
    Do you know what is the input and output decoupling capacitors is customer using? Alternatively, you can also send me customer schematic over email if possible. Thanks.


    Regards,
    Koteshwar Rao
  • 0 in reply to Koteshwar Rao
    TI__Guru 55815 points

    Hi Max,

    Please do let us know what are the input and output capacitance values that customer is using so that I can comment whether the inrush current that customer observed is expected or not. Please also let us know how often does customer product power-up SN6505B throughout its life? For example, like once a day for 10 years?

    Let's assume that the inrush current is exceeding max recommended current of 1A for about 2ms during each power-up once every day for 10 years. In this case, the total accumulated time for which drain current exceeded max recommended current of 1A would be about 7.3 seconds. This does look like a small value and we expect SN6505B to support this current requirement without any issues.

    Let me know if you have any questions, thank you.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 10 points

    The input cap and output cap value as below.Because it will used in EV car, it will be 10 times power up each day.

  • 0 in reply to user5884228
    TI__Guru 55815 points
    Hi Max,

    Thanks for your inputs. 10 times power-up every day for device lifetime should total upto an accumulated time of 73 seconds for which the drain current of SN6505 has exceeded max recommended current but was under absolute maximum spec. 73 seconds over a period of device lifetime is still a very small amount of time and we do not expect this to be an issue for SN6505. Hence it is safe for SN6505 to be used in this customer application. Thanks.


    Regards,
    Koteshwar Rao