Microchip ATF1504AS-10JU44 CPLD: Features, Applications, and Design Considerations

Complex Programmable Logic Devices (CPLDs) remain a cornerstone for glue logic, interface bridging, and control functions in numerous electronic systems. Among these, the Microchip ATF1504AS-10JU44 stands out as a reliable and versatile solution. This 44-pin PLCC device offers a robust combination of density, performance, and ease of use, making it a popular choice for both new designs and legacy system upgrades.

Key Features of the ATF1504AS-10JU44

The ATF1504AS is built on a proven high-performance electrically erasable technology, allowing for complete reconfigurability and design iteration. Its core features include:

High Density Logic: With 32 macrocells and up to 64 inputs, it provides sufficient resources for implementing complex state machines and combinatorial logic.

10ns Pin-to-Pin Logic Speed: The `-10` speed grade ensures that critical paths can operate at high frequencies, making it suitable for timing-sensitive applications.

In-System Programmability (ISP): This feature allows the device to be programmed and reprogrammed while soldered onto the printed circuit board (PCB), drastically simplifying the development, testing, and field update processes.

5.0V Operation: As a 5V-tolerant device, it seamlessly interfaces with a wide range of legacy microcontrollers, peripherals, and bus systems without requiring level shifters.

44-Lead PLCC Package: The Plastic J-Lead Chip Carrier (JU44) package is through-hole solderable, offering mechanical stability and ease of prototyping.

Primary Applications

The ATF1504AS-10JU44 excels in a variety of applications, often serving as the "digital glue" that integrates multiple system components. Common uses include:

Address Decoding: Generating chip select signals for memories and peripherals in microcontroller-based systems.

Bus Interface and Bridging: Interfacing between processors with different bus protocols or voltage levels (e.g., between an 8-bit and a 16-bit bus).

State Machine Control: Implementing control logic for custom sequences, such as power management and system initialization routines.

I/O Expansion and Conditioning: Aggregating and preprocessing I/O signals to offload these tasks from a central processor.

Protocol Conversion: Translating between simple serial protocols like SPI and I²C.

Essential Design Considerations

Successful implementation of the ATF1504AS requires attention to several key areas:

1. Power Supply Decoupling: Like all high-speed digital devices, robust decoupling is mandatory. Place 0.1µF ceramic capacitors very close to the VCC and GND pins to suppress noise and ensure stable operation.

2. JTAG Programming Header: The ISP capability requires a 4-pin JTAG header (TDI, TDO, TMS, TCK) to be included on the PCB layout for connection to a programmer.

3. Pin Management and I/O Standards: While it operates at 5V, careful attention must be paid to sourcing and sinking current (up to 24mA per I/O pin) when driving loads. Ensure that connected devices are 5V tolerant if they are not native 5V parts.

4. Thermal Management: Although power consumption is generally low, it should be estimated using the vendor's tools during design, especially when utilizing a high percentage of macrocells at maximum frequency.

5. Design Security: The device offers a programmable security bit that prevents the readback of the configured design, protecting intellectual property.

ICGOODFIND: The Microchip ATF1504AS-10JU44 is a workhorse CPLD that delivers a solid mix of logic capacity, 5V noise immunity, and design flexibility. Its in-system programmability and familiar architecture make it an excellent choice for consolidating logic, reducing board space, and solving complex interface challenges in industrial control, telecommunications, and computing applications.

Keywords: CPLD, In-System Programmability (ISP), 5V Logic, Macrocell, JTAG