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SN65LVDS352 / output impedance

Toshiyuki
Mastermind 7075 points
Other Parts Discussed in Thread: SN65LVDS352

Hi,

The SN65LVDS352 data sheet shows that the ROUT have a built-in 37ohm resistor. Please let me know if the ROUT require any termination between them and the destination devices.

In addition, would you tell me the meaning of 「-4V to 5V Common-Mode Input Voltage Range」? Is there any problem for DC-coupled?

Best Regards,

Kato

  • 0
    TI__Guru 62920 points

    Hello Kato-san,

    The ROUT outputs do not require any external termination.  Some users choose to include a small (~20 Ohm) series resistance on the output, though.  This helps to provide a better-matched source-side termination for a 50-Ohm single-ended transmission line (which could be useful for long connections) and can also slow down the edge rate a little bit (which can be useful for mitigating EMI/crosstalk).

    The common-mode range spec may be a little misleading.  What it really means is that the device can function normally (i.e., detect valid differential high/low levels) as long as the voltage at each input pin (RIN+, RIN-) is between -4 V and +5 V.  Within this range, the device will detect a +100 mV or greater differential signal as a logic "high" and a -100 mV signal or lower as a logic "low."  It is OK to DC-couple, since the receiver will re-bias the common-mode voltages internally using a high-impedance attenuation/biasing network (illustrated on page 4 of the datasheet).

    Regards,
    Max