The 4 x 4 and 4 x 3 multichip modules (MCM) offer a high-density packaging arrangement for the DS21Q42 T1 Enhanced Quad Framer. Either three (DS21FT42) or four (DS21FF42) silicon die of these devices is packaged in an MCM with the electrical connections as shown in Figure 1-1.
All of the functions available on the DS21Q42 are also available in the MCM packaged version. However, in order to minimize package size, some signals have been deleted or combined. These differences are detailed in Table 1-1. In the 4 x 3 (FT) version, the fourth quad framer is not populated and hence all of the signals to and from this fourth framer are absent and should be treated as No Connects (NC). Table 2-1 lists all of the signals on the MCM and it also lists the absent signals for the 4 x 3.
The availability of both a 12-channel and a 16-channel version allow the maximum framer density with the lowest cost. For example, in a T3 application, two devices (one DS21FF42 and one DS21FT42) provide 28 framers without the additional cost and power consumption of any unused framers that appear in an octal approach.
Key Features
Applications/Uses
16 or 12 completely independent T1 framers in one small 27mm x 27mm, 1.27mm pitch BGA package
Each multichip module (MCM) contains four (FF) or three (FT) DS21Q42 die
Each quad framer can be concatenated into a single 8.192MHz backplane data stream
IEEE 1149.1 JTAG-Boundary Scan Architecture
DS21FF42 and DS21FT42 are pin compatible with DS21FF44 and DS21FT44, respectively, to allow the same footprint to support T1 and E1 applications
300-pin MCM 1.27mm pitch BGA package (27mm x 27mm)
Low-power 3.3V CMOS with 5V tolerant input and outputs
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