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DS15BR401: Hot swap for Bus connection

Satoshi
Guru 19665 points
Part Number: DS15BR401
Other Parts Discussed in Thread: TPD4E05U06, DS90LV804

Customer is using DS15BR401 for Bus connection (1:N).

On application, input sequence is GND ⇒ Signal ⇒ Power supply.

When these hot swappable input, DS15BR401 input side are shocked. 

Please let me know about two points below;

①Is there protection circuit or IC for DS15BR401 input side? 

②In the first place, is DS15BR401 not match the use case of Bus connection?

Best regards,

Satoshi

  • 0
    TI__Mastermind 29655 points
    Hi Satoshi-san,

    1. Is it possible there is a large transient voltage coming on the power supply that is well over VDD? If this is the case, then you may wish to use an ESD diode with minimal capacitance in order not to affect the high-speed signal. One example is the TPD4E05U06, a 4-channel low-capacitance ESD diode.

    2. Looking at the input sequence, I don't think there should necessarily be an issue unless the DS15BR401 input is being exposed to higher than VDD + 0.3 V. Normally, the power supply should not be sent directly to the DS15BR401. Can you provide a schematic of what the customer is doing so we better understand your question about the use case?

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Guru 19665 points

    Michael-san

    Thank you for reply,

    I attached customer schematic, please see below.

    If there any idea, please let me know.

    DS15BR401_schematic.pdf

    【Supplement information】

    ・Below word is mean "LVDS differential impedance : 100Ω pair ".

    ・Attached schematic is old board, DS15BR401 is putting on U107 position.

    　Latest model will replace DS90LV804 to "DS15BR401 & termination resistor". (pin compatible)

    ・Input side is connecting Motherboard (Hot swap) by HM connector. 

    Best regards,

    Satoshi

  • 0 in reply to Satoshi
    TI__Mastermind 43795 points

    Hi Satoshi-san,

    I agree with Michael - the customer may need to consider an external ESD diode in the devices are being zapped.

    The DS90LV804 and the DS15BR401 do have ESD circuitry between the inputs and GND.  As long as the GND connection is low impedance, the internal ESD structure is enabled.

    I did not see anything out of place in the schematic.

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    Guru 19665 points
    Michael-san, Lee-san

    Thank you for reply,
    I was very cleared.

    Best regards,
    Satoshi