Lattice GAL22V10D-7LP: A Comprehensive Technical Overview of the 5ns High-Speed PLD

In the realm of digital logic design, Programmable Logic Devices (PLDs) have been fundamental in bridging the gap between the inflexibility of standard logic ICs and the high cost of full-custom ASICs. Among these, the GAL22V10D-7LP from Lattice Semiconductor stands out as a quintessential and enduringly popular device. This article provides a deep technical dive into this specific component, focusing on its architecture, key features, and the significance of its 5ns maximum propagation delay.

The GAL22V10D is a member of the Generic Array Logic (GAL) family, which revolutionized the PLD market by introducing re-programmability through EECMOS technology. This was a major step forward from its one-time programmable (OTP) predecessors. The "22V10" nomenclature is industry-standard, denoting 22 inputs and 10 output logic macrocells (OLMCs), each of which can be configured as an input or an output. The "D" suffix typically indicates a commercial temperature range device in a plastic leaded chip carrier (PLCC) package, and the critical "-7LP" suffix specifies the 7ns pin-to-pin commercial/industrial speed grade (tPD) and low-power variant.

Architecture and Core Functionality

At its heart, the GAL22V10D features a programmable "AND" array that feeds a fixed "OR" array. This structure is ideal for implementing complex combinational logic and finite state machines. The key to its flexibility lies in its Output Logic Macrocell (OLMC). Each of the 10 OLMCs can be individually configured, allowing designers to define the output structure for each pin. Key configuration options include:

Combinatorial or Registered Output: The output can be directly from the OR array (combinatorial) or passed through a D-type flip-flop (registered) for implementing sequential logic.

Output Polarity: The output can be active-high or active-low, selectable via a programmable XOR gate.

Tri-State Control: Each output's tri-state buffer can be controlled by a product term from the AND array, enabling bidirectional I/O and bus interface applications.

Decoding the -7LP: The Pinnacle of Speed and Efficiency

The "-7LP" speed grade is the most defining characteristic of this variant. The "7" signifies a maximum propagation delay (tPD) of 7.5ns from clock to output (tCO) and a stunning 5ns pin-to-pin combinatorial delay (tPD) under worst-case conditions. This 5ns high-speed performance made it a go-to solution for critical timing paths in high-frequency systems of its era, often replacing multiple smaller-scale integration (SSI) and medium-scale integration (MSI) devices to save board space and increase reliability while maintaining blistering speed.

The "LP" denotes Low Power. Built on Lattice's advanced EECMOS process, the device consumes significantly less power than bipolar PLDs (like PAL devices) with comparable functionality. This combination of high speed and low power consumption was, and in many legacy designs still is, a highly valued characteristic.

Design and Application Considerations

The reprogrammability of the GAL22V10D, facilitated by standard programmers, allowed for rapid prototyping and easy design iterations. Its predictable timing model simplified the design process. Common applications included:

Address Decoding: in microprocessor and memory systems.

Bus Interface Logic: for controlling data flow between different subsystems.

State Machine Implementation: for designing complex control logic.

Glue Logic Consolidation: replacing numerous simple logic gates with a single, integrated device.

ICGOODFIND Summary

The Lattice GAL22V10D-7LP represents a critical juncture in the evolution of programmable logic. It successfully combined the high-density integration of a 22V10 architecture with the game-changing benefits of EECMOS re-programmability, all while delivering blazing-fast 5ns combinatorial performance and low power consumption. It served as a workhorse for a generation of digital designers, providing a perfect balance of flexibility, speed, and cost-effectiveness for a vast array of applications. While modern CPLDs and FPGAs offer far greater capacity, the GAL22V10D remains a legendary device that defined an era of logic design.

Keywords:

1. GAL22V10D

2. 5ns Propagation Delay

3. Programmable Logic Device (PLD)

4. Output Logic Macrocell (OLMC)

5. EECMOS Technology