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SN65LBC173A: Device internal pullup/pulldown resistors

Darren (FAE)
Expert 5483 points
Part Number: SN65LBC173A
Other Parts Discussed in Thread: TB5D2H

The SN65LBC173A has internal pullup/pulldown resistors on both inputs.

From the functional block diagram, it looks like 100kΩ pullup, a series 18kΩ resistor, and then another few kΩ pullup and pulldown.

The other input has the resistors attached to the other rail (GND).

I need to know how a driver like TB5D2H would perform...it only has "high-side transistors" and supports 150Mbps, but my customer only needs to achieve ~ 22Mbps.

With just high-side transistors, pulldown resistors are needed for device to have a proper output when one or the other transistors is OFF.

Is there a SPICE model available for SN65LBC173A?

Is there an equivalent pullup/pulldown resistance value you can help me calculate for each of the two input lines for a Channel?

Please understand I need a reply to this question - sometimes I get pointers to other devices, etc, but for this time in particular I really need an answer to the above

Regards,
Darren

  • 0
    TI__Mastermind 25705 points

    Darren,

    I'm sorry there is no spice model for SN65LBC173A. However I think the schematic is accurate and you can simulate the input stage with several resistors - 100kOhm pull up or pull down, a series 18kOhm to a 2x4kOhm resistor divider (like you pointed out). If you ignore the pull up/down, basically TB5D2H will drive 18kOhm load biased at half Vcc. Looking at TB5D2H datasheet, my speculation is that this scheme may work with 5V.