Microchip Technology AT34C04-SS5M-T

Overview

AT34C04-SS5M-T from Microchip Technology (formerly Atmel) is a 4-Kbit I²C-compatible Serial EEPROM designed for Serial Presence Detect (SPD) in DDR SDRAM modules. It features 512 × 8-bit memory organization, JEDEC JC42.4 (EE1004-v) compliance, reversible software write protection across four 128-byte quadrants, and operates from 1.7V to 3.6V. Its Fast-Mode Plus (FM+) interface supports up to 1 MHz clocking with bus timeout for system robustness.

For engineers reviewing the AT34C04-SS5M-T datasheet, AT34C04-SS5M-T pinout, AT34C04-SS5M-T application, or AT34C04-SS5M-T equivalent, this device serves as a drop-in SPD memory solution for DRAM module configuration storage - requiring attention to quadrant-level RSWP control, page-addressing mode (SPA/RPA), and VHV-tolerant A0 pin handling during write-protection setup.

Technical Context

The AT34C04-SS5M-T implements a dual-halves memory architecture (two 2-Kbit sections), each subdivided into two 128-byte quadrants, enabling legacy EE1002 compatibility via Set Page Address (SPA) and Read Page Address (RPA) commands. It uses I²C FM+ protocol with Schmitt-triggered, noise-filtered SDA/SCL inputs and supports ACK polling for write-cycle completion detection.

Its Reversible Software Write Protection (RSWP) is controlled via dedicated '0110' device address prefix and requires overvoltage (7–10 V) on A0 to activate or clear protection states. The device enters low-power Standby Mode after Stop condition or power-up, drawing ≤4.0 µA at 3.6 V.

Key Specifications

Pinout & Package

AT34C04-SS5M-T is packaged in an 8-lead SOIC (JEDEC MS-012, package code SS5M). Pin functions are electrically defined and validated per Atmel-8827G datasheet Section 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT24C04C-SSHM-T and M95040-DRMN6TP/K, the AT34C04-SS5M-T uniquely delivers JEDEC SPD compliance, reversible quadrant-level write protection, and bus timeout - making it irreplaceable in DDR memory module applications where standards adherence and field-programmability are mandatory.

Availability

AT34C04-SS5M-T is available at Aetrix Electronics and suitable for DDR memory module manufacturing, industrial DIMM programming stations, and legacy SPD upgrade programs requiring stable component supply, long-lifecycle support, and RoHS-compliant green packaging.

Supply support for AT34C04-SS5M-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 acquired Atmel in 2016 and maintains full product support, documentation, and qualification for legacy Atmel serial EEPROMs including the AT34C04 family.

The AT34C04 product line was engineered specifically for JEDEC-compliant Serial Presence Detect in DRAM modules - balancing SPD protocol fidelity, field-programmability, and industrial-grade reliability.

FAQ

What is the function of the A0 pin on the AT34C04-SS5M-T beyond device addressing?

The A0 pin on the AT34C04-SS5M-T serves a dual role: it is both the LSB of the 3-bit hardware device address and the overvoltage-enable input for Reversible Software Write Protection (RSWP). To set or clear RSWP, A0 must be driven to 7–10 V (VHV) while issuing specific I²C commands with device address prefix '0110'. This VHV tolerance is unique to the AT34C04-SS5M-T and is not present in standard I²C EEPROMs like the AT24C04C-SSHM-T.

Does the AT34C04-SS5M-T support true 1 MHz I²C operation across its full voltage range?

Yes, the AT34C04-SS5M-T supports 1 MHz I²C Fast-Mode Plus (FM+) operation at VCC ≥ 2.2 V, as specified in Table 5-2 of the datasheet. At VCC < 2.2 V, maximum clock frequency is limited to 400 kHz. The device includes integrated Schmitt triggers and noise filters on SDA/SCL to maintain signal integrity at high speeds, and its tLOW/tHIGH timing parameters are guaranteed for 1 MHz operation under valid supply conditions.

How does the AT34C04-SS5M-T achieve backward compatibility with 2-Kbit EE1002 SPD devices?

The AT34C04-SS5M-T achieves backward compatibility through its Set Page Address (SPA) and Read Page Address (RPA) command mechanism. By default, SPA = 0 after power-up, restricting access to the lower 256 bytes (Quadrants 0 and 1) - matching the memory map of legacy 2-Kbit devices. Firmware need not change; only the AT34C04-SS5M-T's extended capacity becomes accessible when SPA = 1 is explicitly set.

Is the NC pin on the AT34C04-SS5M-T internally connected or safe to tie to ground?

The NC pin on the AT34C04-SS5M-T is not bonded to the die and is electrically unconnected. As confirmed in Table 1-1 of the datasheet, it may be safely left floating or tied to GND based on PCB layout requirements - for example, to improve mechanical stability or reduce EMI susceptibility. No functional impact occurs regardless of NC pin termination.

What is the purpose of the bus timeout feature in the AT34C04-SS5M-T, and how is it triggered?

The bus timeout feature in the AT34C04-SS5M-T prevents system lockup by releasing the SDA line if SCL remains low for longer than 25–35 ms (tOUT). This condition commonly arises from bus contention, faulty masters, or noise-induced clock stretching. Once triggered, the AT34C04-SS5M-T resets its interface state and resumes readiness for a new Start condition - ensuring recoverability without requiring power cycle or hardware reset.