25CS320T-E/Q4B

Overview

The Microchip Technology 25CS320 is a 32-Kbit (4,096 x 8 bit) SPI Serial EEPROM featuring a 32-byte page size and self-timed write cycles up to 4 ms. It operates within a voltage range of 1.7V to 5.5V, supporting clock frequencies up to 20 MHz at VCC ≥ 4.5V. The device includes a Security Register with a preprogrammed 128-bit serial number and 32 bytes of user-programmable lockable ID space. Built-in ECC logic corrects single-bit errors per four-byte readout, while undervoltage lockout detection protects against brown-out events.

Feature Summary

• Integrated Security Register containing a factory-programmed 128-bit unique serial number and a user-programmable, lockable ID page for asset tracking and data protection.
• Built-in Error Correction Code (ECC) logic that automatically corrects single-bit read errors within four-byte sequences and provides status reporting via the STATUS register.
• Configurable Enhanced Write Protection Mode allowing independent segmentation of memory into partitions with distinct software or hardware protection behaviors.
• Programmable Undervoltage Lockout Detection circuit that inhibits write operations when supply voltage drops below a configurable threshold to prevent data corruption.

Applications

• Automotive systems requiring AEC-Q100 qualified nonvolatile memory with high reliability and temperature resilience.
• Industrial control applications needing secure device identification and robust data retention under varying power conditions.
• Consumer electronics utilizing SPI interfaces where compact 8-lead packages and low standby current are critical.
• Systems requiring hardware-enforced write protection for critical configuration data using legacy or enhanced partition modes.

Procurement Notes

Verify the specific suffix codes in the ordering information to confirm the exact package type, temperature grade, and tape/reel specifications required for your assembly process. Ensure compatibility with your system's SPI clock rates and voltage levels before finalizing procurement. Cross-reference the datasheet revision to confirm feature availability and electrical characteristics match your design requirements.

Selection Notes

Select this component when a globally unique serial number is required for manufacturing serialization without external programming steps. Choose the Extended (E) or High-Temperature (H) variants if operation above +85°C is necessary. Consider the Enhanced Write Protection mode if complex, partition-specific access controls are needed beyond standard block protection. Verify that the 32-byte page size aligns with your application's write granularity requirements.

Part Context

The 25CS320 belongs to Microchip’s CS series of SPI Serial EEPROMs, designed for backward compatibility with older 25AA/25LC and AT25320B devices. It expands upon previous generations by adding integrated security features and advanced write protection schemes. The device is optimized for environments demanding high endurance and long-term data retention, serving as a drop-in replacement for legacy parts while offering enhanced functionality.

Replacement Considerations

The datasheet explicitly states backward compatibility with the 25AA320A, 25LC320A, and AT25320B. When replacing these parts, verify that the host controller supports the new Enhanced Write Protection commands if utilized. Ensure the SPI timing parameters meet the minimum setup and hold times specified in the AC characteristics table.

FAQ

How does the built-in ECC logic function?

The ECC logic can correct up to one incorrectly read bit within a four-byte readout sequence. It also sets a flag in the STATUS register to indicate if an error was detected and corrected during the most recent memory array read.

What is the difference between Legacy and Enhanced Write Protection modes?

Legacy mode uses Block Protection bits in the STATUS register to protect quarter, half, or the entire array. Enhanced mode allows the user to define independent memory partitions, each with unique protection behaviors that can be set via software or the WP pin.

Can the user-programmable section of the Security Register be modified after locking?

No. Once the user-programmable 32-byte ID page is permanently write-protected via a software sequence, it cannot be altered again.