Lattice GAL22V10D-5LJN: Architecture, Key Features, and Application Design Considerations

The Lattice GAL22V10D-5LJN represents a specific member of the widely adopted Generic Array Logic (GAL) family of programmable logic devices (PLDs). As a 5-nanosecond, 24-pin, low-power CMOS device in a plastic J-lead chip carrier (PLCC) package, it serves as a powerful and flexible solution for integrating complex combinational and sequential logic, often replacing multiple standard logic ICs on a circuit board.

Architecture and Core Logic Block

The architecture of the GAL22V10D is built around a programmable AND array feeding into a fixed OR array. The "22V10" designation is key: it signifies 22 inputs and 10 output logic macrocells (OLMCs). This structure allows for the implementation of sum-of-products logic functions.

Each of the ten output pins is controlled by a sophisticated OLMC. The configurability of these macrocells is the cornerstone of the device's flexibility. Each OLMC can be individually programmed to operate in various modes:

Combinational Mode: The output is solely a function of the current input states.

Registered Mode: The output is stored in a D-type flip-flop, synchronizing the output to the global clock signal (on pin 1). This is essential for implementing state machines and counters.

Complex Mode: Allows for configuration as an input or a combinatorial output with feedback.

This programmability is achieved through a architecture matrix and fuse map, which is defined by the user using hardware description languages (HDLs) or schematic entry and then "fused" into the device using a programmer.

Key Features and Advantages

The GAL22V10D-5LJN offers several defining characteristics that have ensured its longevity in digital design:

High Speed: The `-5` suffix denotes a maximum propagation delay of 5 nanoseconds, making it suitable for high-performance logic applications.

Re-programmability: Unlike one-time programmable (OTP) PALs, GAL devices are based on E²CMOS (Electrically Erasable CMOS) technology. This allows the device to be erased and reprogrammed thousands of times, drastically reducing development time and cost.

Low Power Consumption: The CMOS technology ensures very low power consumption, both in active and standby modes, which is critical for power-sensitive designs.

Full Programmability: The output logic macrocells can be configured for registered or combinatorial operation, and output polarity is also programmable, simplifying logic minimization.

100% Testability: The internal logic design provides complete access for functional testing, ensuring high fault coverage.

Critical Application Design Considerations

Successfully integrating the GAL22V10D-5LJN into a design requires careful attention to several factors:

1. Power-On Reset (POR): The internal registers have a defined power-on reset state, which is crucial for ensuring a known startup condition in state machines. Designers must verify this behavior and design their reset circuitry accordingly.

2. Clock and Input Management: Pin 1 is dedicated as a global clock input for all registered macrocells. Its signal integrity is paramount. Input signals must meet specified setup and hold times relative to this clock to ensure reliable synchronous operation.

3. Fan-Out and Loading: While the outputs have strong drive capabilities, the total capacitive load from connected inputs must be calculated to ensure signal integrity and avoid exceeding maximum rise/fall time specifications.

4. Thermal Management: Although a low-power device, the PLCC package has a specified thermal resistance. Designers must ensure the operating ambient temperature and power dissipation do not cause the junction temperature to exceed its limit.

5. Design Security: The device contains a programmable security fuse. Once programmed, this fuse prevents the programmed pattern from being read back, protecting intellectual property from competitors. This should be activated only after final design verification.

ICGOOODFIND

The Lattice GAL22V10D-5LJN remains a highly effective and cost-efficient PLD for consolidating glue logic, implementing fast state machines, and creating custom logic interfaces. Its blend of high speed, low power, and complete reprogrammability offers a perfect balance for a vast array of digital design tasks, from prototyping to production.

Keywords:

Programmable Logic Device (PLD)

Output Logic Macrocell (OLMC)

E²CMOS Technology

Propagation Delay

Global Clock