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Need confirmation for SN65LBC184D

Dibin Mathew
Intellectual 330 points
Other Parts Discussed in Thread: TXB0102

Hi,

We are using SN65LBC184D(Transceiver) and TXB0102DCUR(Level translator) for UART interface. While doing logic analysis, the interface is failing. Our circuit connection is as explaned below.

Pin 1(Pin name:R) of SN65LBC184D is connected to pin 8(Pin name: B1) of TXB0102DCUR and VCCB  of TXB0102DCUR is connected to 5V and VCCA is connected 3.3V  and VCC of SN65LBC184D connected to 5V.

As per TXB0102DCUR datasheet, Vih(min) is 0.65*VCCI(3.25V) but Voh(min) of SN65LBC184D is at 2.8V. While SN65LBC184D is driving TXB0102DCUR, we will have negative margin.(Voh-Vih).

Plz confirm whether we can use this devices together or  the output of transceiver can be a open drain configuration, so that by using pullup resistor we can able to slove this.

  • 0
    TI__Expert 4705 points

    Hi,

    For TXB0102DCUPR, it needs 2mA current driver capability. Based on the datasheet of SN65LBC184D, it has the Voh minimum with 2.8V when 8mA current source. so could you please get the Voh value for SN65LBC184D when it provide 2mA source current for the recevier. if it can reach to 3.25 V, then it will be Ok to connect them as your design.

    If the SN65LBC184D Voh can not reach to 3.25V even with 2mA current source. I think we can use your solution which config your transceiver to be the open drain configuration output (not sure SN65LBC184D can be, you need to check this), and add one pull up resistor. but please be careful to chose this pull up resistor, it will decrease Vol of your transceiver, if you use SN5LBC184D and config it with open drain output, the pull up resistor will about  between 1Kohm and 2Kohm, at the same time, you need to check he RC time for the rising time of the transceiver high output, to meet the Δt/Δv for TXB0102. but  if you choose antoher transceiver , you need to check the current sink capability of that transceiver, make sure not less than 4mA. the precondition of this method is for one directional signal transtion, if the signal is bidriecitonal, we can not use this method.

    BR
    Junjie 

    BR

    junjie

  • 0 in reply to Junjie Mai
    Intellectual 330 points

    HI,

    Do any one have Pspice model for SN65LBC184D . If yes plz share.

    We need the details of internal TVS diode used for this IC. We are trying to create the Pspice model.

    We need the following values for the internal TVS diode for creating Pspice model.

     1)      Clamping voltage(CL):

    2)      Reverse standoff voltage(Vwm):

    3)      Break down voltage(Vbr):

    4)      Maximum standby current(Id@Vwm):

    5)      Maximum peak pulse current(Ipp):

    6)      Working inverse blocking voltage(Vwib):

    7)      Inverse blocking leakage current(Iib@Vwib):

    8)      Peak inverse blocking voltage(Vpib):

    Thanks and Regards

    Dibin Mathew