Logic Design for Array-Based Circuits

by Donnamaie E. White

Sizing the Design - Selecting the Array

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

IF INPUT IS OF TYPE:			OUTPUT CAN BE ANY OF:
TTL	ECL 10K	ECL 100K	TTL	ECL 10K	ECL 100K
X			X	X	X
	X		X	X	X
		X	X	X	X
X	X		X	X	X
X		X	X	X	X

Table 3-13 TTL OUTPUT OPTIONS

standard TTL

open-collector

three-state or 3-state also called tri-state

standard TTL output bidirectional

open-collector output bidirectional

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

Output Options
ECL 10K, 50 ohm termination
ECL 100K, 50 ohm termination
ECL 10K, 25 ohm termination
ECL 100K, 25 ohm termination
ECL 10K, 50 ohm termination bidirectional
ECL 100K, 50 ohm termination bidirectional
CML outputs (> 600MHz), ECL's version of an open-collector
On-chip 50 ohm series termination ECL 10K
On-chip 50 ohm series termination ECL 100K
On-chip 100 ohm series termination ECL 10K
On-chip 100 ohm series termination ECL 100K
Darlington ECL 10K, 50 ohm termination
Darlington ECL 100K, 50 ohm termination
Darlington ECL 10K, 25 ohm termination
Darlington ECL 100K, 25 ohm termination
Darlington ECL Hi-Z 10K
Darlington ECL Hi-Z 100K
Darlington On-chip 50 ohm series termination ECL 10K
Darlington On-chip 50 ohm series termination ECL 100K
Darlington On-chip 100 ohm series termination ECL 10K
Darlington On-chip 100 ohm series termination ECL 100K

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