The differences between various types of the AT29C256 (a 256Kbit [32K x 8] 5-volt only Flash memory chip) primarily relate to speed, packaging, temperature ratings, and manufacturing reliability. While the core memory functionality remains the same, these factors determine the best fit for specific applications.
Here are the key areas of variation based on part number suffixes:
1. Access Speed (Speed Ratings)
The numbers following the hyphen (e.g., 90, 12, 15) indicate the maximum access time in nanoseconds (ns).
- 70/700: 70ns (Fastest)
- 90/900: 90ns
- 12/120: 120ns
- 15/150: 150ns
- Faster chips can be used in place of slower ones, but not always vice versa.
2. Package Types
The package affects how the chip is soldered or socketed onto a board.
- P (PDIP): 28-pin Plastic Dual Inline Package (ideal for through-hole breadboards).
- J (PLCC): 32-pin Plastic Leaded Chip Carrier (surface mount or socket).
- T (TSOP): 28-lead Thin Small Outline Package (smaller surface mount).
3. Temperature Range and Reliability
Suffixes after the package type indicate the environmental rating.
- C: Commercial (0°C to 70°C).
- I: Industrial (-40°C to +85°C).
- RoHS Compliance: Some newer versions are RoHS compliant (lead-free), whereas older stock might not be.
4. Part Number Breakdown Example (AT29C256-90TI)
- AT29C256: The device type (256Kbit Flash).
- 90: 90ns access speed.
- T: TSOP Package.
- I: Industrial Temperature Range (-40 to +85°C).
- -T: Tape and Reel packaging.