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?