There are instances when a system designer is utilizing numerous components whose power supply levels don’t match. In most cases, AC coupling of the parts together while incorporating resistive networks to set proper voltage bias points if needed is utilized. This kind of strategy doesn’t work though when the signaling in between the two parts is unbalanced. A special active solution is needed in the case when two parts are at different power supplies, but they need to be DC coupled together.
The ASNT3112-KMC from ADSANTEC is a broadband up to 32Gbps dual channel linear signal level down shifter. The logic level converter takes either data (digital or analog) or clock signals and shifts them from a positive reference power supply of +3.3 (Vee = 0V) to a negative reference power supply of 0V (Vee=-3.3V). The IC’s I/Os feature on chip 50ohm termination and can be used single-ended or differential either DC or AC coupled.
The differential gain of the linear signal level down shifter is approximately 0dB. An up to 800mV peak to peak differential input can be used on both of the parallel identical channels.
The logic level converter was built to satisfy end-users who need the voltage level down shifting capability between two parts functioning together, but can’t use AC coupling to do so. The ASNT3112-KMC allows system designers to connect parts operating on different power supplies to be DC coupled. The main reasons where AC coupling is not a solution is when analog data is being processed or the data signal is unbalanced (for a 2-level NRZ signal that means not an even number of 1s and 0s).
The small compact part is housed in a high speed custom QCFP metal ceramic package and adds very little jitter to the input signal. The package is easier to solder down to any sort of evaluation board including PCB.