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Vih and Vil of FX_SD input signal to DP83620

Steven Martin
Prodigy 30 points
Other Parts Discussed in Thread: DP83620

The datasheet for the DP83620 is vague regarding the Vih and Vil levels for the FX_SD input, just that it is PECL compatible.  There are also strong admonishments not to strap the pin to VCC or ground except through a 2.2K resistor.  The transceiver--which I cannot change--provides a signal detect signal with Vol=0.4 and Voh=2.4 (normal TTL).  I don't know what type of driver is actually driving.  Is there any way to connect a TTL/CMOS output to the FX_SD input without using a TTL to PECL translator?  For example, could I drive the FX_SD input with an LVC buffer through a 2.2K series resistor?

  • 0
    TI__Mastermind 31600 points

    Steven,

    The FX_SD input expects LVPECL levels and are often specified as negative voltages from the positive rail.  Using a TTL level driver would not be recommended.  However, the input can accept CMOS levels.  I would suggest using CMOS levels or using a TTL to PECL translator.

    Patrick