AT43USB325E-AC

Overview

The AT43USB325E-AC is an 8-bit AVR microcontroller featuring a USB hub with one embedded function and four external ports. It includes 16 KB of downloadable SRAM program memory, automatically written from an external serial EEPROM during power-on reset, and 512 bytes of data SRAM. The device operates at 5V with an on-chip 3.3V regulator and utilizes a 6-MHz oscillator with a PLL to generate the required 12 MHz USB clock. Key peripherals include two timer/counters, four LED drivers, and GPIO pins configured for keyboard matrix scanning.

Feature Summary

• AVR 8-bit RISC architecture with 83 ns instruction cycle time
• Integrated USB Hub with one attached function and four external ports
• 16 KB downloadable SRAM program memory loaded via SPI from external EEPROM
• Keyboard controller support with 20x8 matrix scan inputs and pull-up resistors

Applications

• Multimedia USB keyboards
• USB keyboard controllers with embedded hubs
• Consumer page supporting USB devices

Procurement Notes

Verify the presence of an external serial EEPROM (e.g., AT25HP256/512) as the AT43USB325E requires it for program memory initialization during power-on reset. Confirm the package type is 64-lead LQFP and ensure the AC suffix corresponds to the specified operating temperature range. Check pin compatibility if replacing the masked ROM version (AT43USB325M).

Selection Notes

Select the AT43USB325E over the AT43USB325M when field-programmable or updatable firmware is required, as the E variant uses downloadable SRAM. Ensure the design accommodates the specific external capacitor requirements: 2.2µF for CEXT1 and 0.33µF for CEXT2. Verify that the application does not require idle mode support, which is not available in this family.

Part Context

This component belongs to the AT43USB325 family, which integrates an AVR core with specialized USB hardware for keyboard applications. The 'E' suffix denotes the SRAM-based program memory version, while 'M' indicates masked ROM. Both versions are pin, function, and binary compatible, allowing for flexible manufacturing choices based on volume and update needs.

Replacement Considerations

The AT43USB325M-AC is a direct functional replacement if firmware updates are not required, as both are binary compatible. Ensure the external EEPROM interface is disconnected or unused when substituting the M variant.