Core features and memory map for firmware planning
The Microchip AVR64DB28T-I/SS is an 8-bit AVR microcontroller built around the AVR core running at up to 24 MHz. The 512-byte EEPROM array endurance is rated for 100k write/erase cycles typical for the AVR DB family, which suits wear-leveled parameter storage in a ten-year product life. The 8 KB SRAM holds the stack and runtime data for typical control loops; if your application uses a TCP/IP stack or large lookup tables, budget carefully — this is not a memory-rich part. The 64 KB Flash should be enough for moderate firmware with bootloader support; the AVR DB series supports self-programming for in-application updates.
Package and I/O: 28-pin SSOP with 21 GPIOs
The 28-SSOP package (5.30 mm wide, 0.209" pitch) is a compact surface-mount body suited for two-layer boards where routing density is moderate. Of the 28 pins, 21 are available as general-purpose I/O. The remaining pins serve power, ground, and the programming/debug interface (UPDI). The 21 I/O count limits your external peripherals — if you need more than 21 signals, step up to a 44-pin TQFP variant in the same AVR DB family. The SSOP footprint is compatible with standard 0.65 mm pitch soldering processes. MSL level is 3 out of the bag — bake before reflow if the moisture-barrier bag has been open longer than 168 hours at <30 °C / 60% RH.
Peripherals and analog integration
The ADC is adequate for reading multiple analog sensors (thermistors, potentiometers, current-sense resistors) through a multiplexer; the DAC can generate a simple analog output voltage without an external converter. The part also includes a PWM module, brown-out detect, power-on reset, and watchdog timer — the usual complement for standalone embedded control.
It is ROHS3 compliant. There is no official second source listed in the AVR DB family, but the pin-compatible AVR32DD28T-I/SS (same 28-SSOP package, 32 KB Flash, 24 MHz) offers a drop-in alternative with fewer Flash and SRAM resources for cost-sensitive BOM lines.