JAJSSV2G March 2011 – January 2024 DAC3482
PRODUCTION DATA
In byte-wide data interface format, the data is transferred via the D[7:0]P/N LVDS port and the D[15:8]P/N LVDS port are not active. The non-active, unused pins can be left unconnected (floating) or connected to a nominal, differential LVDS active HIGH or active LOW voltage. The choice of LVDS connections to the unused LVDS ports will not affect the operations of LVDS receiver, digital functions such as mixers, NCO, and QMC, and analog output stage. However, if the system designer wishes to implement the following features in the end system, the designer may need to connect the unused ports to a known logic value:
The following example allows the termination of the unused LVDS ports to a known logic HIGH value. As shown in Figure 6-35, The design involves the connection to the DIGVDD rail and one RSET resistor to bias the positive terminals of unused LVDS ports to be 1.2V and negative terminals of unused LVDS ports to 1V. The design keeps the minimum common mode input voltage of the LVDS input to be above 1V, and keeps the differential LVDS voltage to be 200mV. Since the design expects the differential voltage on the unused ports to be static, the differential LVDS voltage can be as low as 100mV to maintain a logic HIGH. Refer to Section 5.6 for details of LVDS Input requirements.
Depending on the DAC3482 functionality required, additional unused LVDS ports such as FRAMEP/N, SYNCP/N, or PARITYP/N can also be left unconnected (floating) or connected to a nominal, differential LVDS active HIGH or active LOW voltage. The usage of these ports depends mainly on the FIFO synchronization settings and parity checking settings. The unused FRAMEP/N, SYNCP/N, or PARITYP/N ports can be connected in parallel with the unused LVDS data port with adjustments to the RSET resistor value.