Tech Brief No. 6 Multi-Channel T1/E1 Solutions Tom Spencer, Product Manager, Telecom Products
Space Cost & Comparison Single-Point Failure Flexibility Conclusion Appendix A		Recent advances in semiconductor integration now allow more than one T1 or E1 port to be placed on the same card. T1 and E1 integrated circuit solutions have also been moving toward higher integration both vertically (the line interface function merging with the framing function) as well as horizontally (dual or quad line interface and dual or quad framers). As with all designs, the critical parameters are space and cost. This white paper addresses these two key issues based on an assumed quad port design. To examine all of the possible options, we will look at the available solutions from a number of vendors which are listed anonymously below. For brevity, line interface is abbreviated LIU.

Vendor Solutions Offered PCB Space Required for the IC Dallas 1. Single Short and Long Haul LIU + Framer in 100-pin TQFP 2. Quad Framer in 128-pin TQFP 0.63" x 0.63" 0.63" x 0.87" L 1. Single Short Haul Only LIU in 28-pin PLCC 2. Dual Short Haul Only LIU in 44-pin PLCC 0.49" x 0.49" 0.69" x 0.69" C 1. Single Short Haul Only LIU in 28-pin PLCC 2. Dual Short Haul Only LIU in 64-pin TQFP 0.49" x 0.49" 0.47" x 0.47" P 1. Single Short Haul Only LIU + Framer in 80-pin PQFP 2. Quad Framer in 128-pin PQFP 3. Quad Short Haul Only LIU in 128-pin PQFP 0.68" x 0.68" 0.68" x 0.91" 0.68" x 0.91" A 1. Quad Short Haul Only LIU in 100-pin BQFP 0.90" x 0.90" S 1. Single Short Haul Only LIU + Framer in 80-pin PQFP 0.68" x 0.68" Note: to convert inches to millimeters, multiply by 25.4. Space & Cost Comparison Multi-channel designs will place a premium on PCB real estate. We will examine a number of options to compare the PCB board space required for each and the costs associated with each. To keep each design option on equal footing, we will assume that each design uses a combination receive and transmit SMD transformer that has a footprint of 0.50" x 0.40" and that the transformer cost $3 each. Also we will assume that each design will use SMD crystals that occupy 0.30" x 0.20" of PCB space and cost $3 apiece. Finally, we will assume that each design needs 0.8" x 0.8" of PCB space per port for bypass capacitors, termination resistors, over-voltage protection devices, and other associated passive devices. No cost will be assigned to these components. The price for the integrated circuits was based on published prices at the volume level of 10K ports per year (i.e., 2.5K cards per year). Option Configuration PCB Space Required in In.² Total Four Port Cost A 4 Single Short & Long Haul LIU + Framer from Dallas 5.0 $95 B1 4 Single Short Haul Only LIU + Framer from Vendor P 5.3 $107 B2 4 Single Short Haul Only LIU + Framer from Vendor S 5.7 $140 C1 1 Quad Framer from Dallas + 2 Dual Short Haul Only LIU from Vendor C 4.4 $105 C2 1 Quad Framer from Vendor P + 2 Dual Short Haul Only LIU from Vendor C 4.5 $115 D1 1 Quad Framer from Dallas + 4 Single Short Haul Only LIU from Vendor C or L 5.1 $114 D2 1 Quad Framer from Vendor P + 4 Single Short Haul Only LIU from Vendor C or L 5.2 $124 E1 1 Quad Framer from Dallas + 1 Quad Short Haul Only LIU from Vendor A 4.8 $115 E2 1 Quad Framer from Vendor P + 1 Quad Short Haul Only LIU from Vendor A 4.9 $125 E3 1 Quad Framer from Vendor P + 1 Quad Short Haul Only LIU from Vendor P 4.7 $107 Single-Point Failure Another issue to be considered in a multi-channel T1/E1 design is the effect of a single-point failure on the design. When using a horizontally integrated solution (i.e. a quad/dual LIU or a quad/dual framer), a single-point failure in one integrated circuit will affect either two or four T1 or E1 channels. Whereas with the vertically integrated solution, a single-point failure will only affect one T1 or E1 communications channel. Flexibility By their very nature, vertically integrated solutions have a flexibility advantage over horizontally integrated solutions. The vertical solutions can support any number of ports not just increments of four. For example, with the vertical solution, it is quite easy and cost effective for a single PCB design to support a stuffing option for both a quad port and a dual port application. Conclusion The differences in PCB board real estate between a horizontally integrated solution and a vertically integrated solutions are small, 10% or less. Vertically integrated solutions have advantages over horizontally integrated solutions in areas of cost, survivability to single-point failures, and flexibility. Appendix A: Visual Comparison of a Vertically Integrated Solution vs. a Horizontally Integrated Solution Below is an actual size comparison of a quad port T1/E1 design using both a vertically integrated solution from Dallas Semiconductor and a horizontally integrated solution from PMC-Sierra.