Microchip Technology AT24CSW040-STUM-T

Overview

AT24CSW040-STUM-T from Microchip Technology is a 4-Kbit I²C-compatible serial EEPROM with integrated security register, software write protection, and industrial-grade operation (−40°C to +85°C). It delivers 512 × 8-bit memory organization, 1 MHz Fast Mode Plus support, ultra-low standby current (0.8 μA max), and factory-programmed 128-bit unique serial number for secure device identification in embedded systems.

For engineers reviewing the AT24CSW040-STUM-T datasheet, AT24CSW040-STUM-T pinout, AT24CSW040-STUM-T application, or AT24CSW040-STUM-T equivalent, this page provides verified electrical specs, package mapping to SOT23-5, security register architecture, write-protection configuration options, and real-world use cases in firmware authentication and calibration storage.

Technical Context

The AT24CSW040-STUM-T operates as an I²C client device with fixed hardware address and supports Standard (100 kHz), Fast (400 kHz), and Fast Mode Plus (1 MHz) clock rates across 1.7V–3.6V supply. Its internal architecture includes dual EEPROM arrays - main 4-Kbit array with five-level software write protection and a dedicated 256-bit security register containing preprogrammed 128-bit serial number plus 16-byte user-programmable section.

Communication uses open-drain SDA/SCL with Schmitt-trigger inputs and spike filtering; WP pin enables hardware-level write inhibition on SOT23-5 package only. Power-on reset ensures reliable initialization, and self-timed write cycles complete within 5 ms maximum without external timing control.

Key Specifications

Pinout & Package

AT24CSW040-STUM-T is packaged in 5-lead SOT23 (STUM suffix), with pin 5 designated as Write-Protect (WP). This package variant includes the WP pin; the WLCSP version does not. Pin functions are electrically validated per Microchip DS20006426B.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar serial EEPROM applications.

Compared with AT24CSW040-STUM-T, both alternatives omit the 128-bit factory serial number and 16-byte programmable security section, limiting their suitability for secure boot, anti-counterfeiting, or regulatory-compliant calibration storage - key differentiators enabled exclusively by the CSW series architecture.

Availability

AT24CSW040-STUM-T is available at Aetrix Electronics and suitable for secure firmware authentication, calibration data storage, asset tracking tags, and smart meter configuration requiring stable component supply and long-term lifecycle support.

Supply support for AT24CSW040-STUM-T includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Microchip Technology Inc. is a leading provider of microcontrollers, analog components, and memory solutions, serving automotive, industrial, and consumer markets with high-reliability silicon and development tools.

The AT24CSW040-STUM-T belongs to Microchip's CSW-series serial EEPROM product line, designed specifically for applications demanding hardware-rooted device identity, field-updatable secure storage, and robust operation in space- and power-constrained embedded systems.

FAQ

What is the function of the WP pin on the AT24CSW040-STUM-T?

The WP (Write-Protect) pin on the AT24CSW040-STUM-T is a hardware-level control that, when driven high to VCC, inhibits all write operations to both the main 4-Kbit EEPROM array and the 256-bit security register. When connected to GND or left floating (internally pulled down), normal read/write functionality is enabled. This pin is present only on the SOT23-5 package (STUM), not on WLCSP variants, and is critical for preventing accidental or malicious memory corruption during system operation or firmware updates.

Does the AT24CSW040-STUM-T support 1 MHz I²C communication?

Yes, the AT24CSW040-STUM-T fully supports I²C Fast Mode Plus at 1 MHz across its entire operating voltage range of 1.7 V to 3.6 V. This capability allows high-speed parameter loading and firmware verification in time-critical applications. The device meets AC timing requirements including tLOW = 500 ns, tHIGH = 400 ns, and tR/tF ≤ 100 ns, enabling interoperability with modern microcontrollers and SoCs without bus slowdowns or timing margin compromises.

How is the 128-bit serial number in the AT24CSW040-STUM-T used and protected?

The 128-bit serial number in the AT24CSW040-STUM-T is factory-programmed and permanently locked during Microchip's production process - it resides in a read-only section of the security register and cannot be altered, erased, or overwritten. It consumes no user memory space and is globally unique across all CS and CSW series EEPROMs. Applications access it via standard I²C reads starting at security register address 0x00; its immutability makes it ideal for cryptographic key derivation, secure boot binding, and regulatory device registration without external provisioning infrastructure.

Can the AT24CSW040-STUM-T operate reliably at 1.7 V?

Yes, the AT24CSW040-STUM-T is fully specified for operation at 1.7 V, including all I²C modes (Standard, Fast, and Fast Mode Plus), active and standby current limits, and write endurance. At 1.7 V, ICC1 (read current) is characterized up to 0.3 mA and ISB (standby current) remains ≤0.4 μA, enabling direct integration into energy-harvesting and coin-cell-powered systems. The device's low-voltage design eliminates the need for level shifters when interfacing with 1.8 V logic families.

What is the difference between the main EEPROM array and the security register in the AT24CSW040-STUM-T?

The main EEPROM array in the AT24CSW040-STUM-T is a 4-Kbit (512 × 8) user-accessible memory block supporting byte/page writes and configurable software write protection. The security register is a separate 256-bit structure: first 128 bits contain a factory-programmed, read-only unique serial number; next 128 bits provide 16 bytes of user-programmable EEPROM that can be independently write-protected. Both regions are accessed via distinct I²C address ranges and serve complementary roles - general storage vs. identity and critical data assurance.