Logic Design for Array-Based Circuits
by Donnamaie E. White
Copyright © 1996, 2001, 2002 Donnamaie E. White
Sizing the Design - Selecting the Array
Last Edit July 22, 2001
Example: AMCC interface options
For all AMCC arrays, TTL and ECL translators are included in the I, O, or I/O cells for external interfacing to both ECL and TTL. Each I, O, or I/O cell can be configured to be either TTL, ECL 10KH, ECL 10K, ECL 100K or as a power or ground pad. I/O cells can usually be used for input macros, output macros or bidirectional macros. Table 3-12 shows the possible I/O combinations allowed on AMCC arrays while Table 3-13 details the TTL output options and Table 3-14 the ECL output options.
Table 3-12 AMCC Interface Combinations
Table 3-13 TTL OUTPUT OPTIONS
The 3-state outputs and TTL bidirectional macros have an enable pin that is either restricted to being driven by a specific macro type (a 3-state enable driver) or unre stricted and driveable by any internal-level signal. The restriction depends on the array and on the mode (100% TTL or Mixed ECL/TTL) of the circuit.
Table 3-14 ECL Output Options
From CML forward in the above list are types identified as possible for the Q20000 Series. Standard ECL 10K, 100K, CML and Darlington outputs were in the first re lease of the macro library for the series.
Power supply options
In addition to the types of interface required, the power supply or power supplies to be used should be compared to the supplies allowed for the array. The supplies, the number of fixed power and ground pads and their locations should be reviewed for their applicability to the design in question.
There is often a need to have an array interface with several types of I/O while keeping power supply requirements in line with what is already provided on the target PCB (printed circuit board). This can lead to operation of a technology with non-standard voltages.
Effects on Parametrics
When non-standard voltages are used, such as -4.5V with ECL 10K and -5.2V with ECL 10K, the DC parametrics for the array will be affected. The data sheet for the array series will call out the parametrics for standard supplies.
Copyright @ 2001,
2002 Donnamaie E. White, White