Microchip Technology AT24C128B-PU

Overview

AT24C128B-PU from Microchip Technology (formerly Atmel) is a 128 Kbit serial EEPROM IC organized as 16,384 × 8 bits, supporting 1.8 V to 5.5 V operation, 400 kHz (1.8 V) / 1 MHz (5.5 V) I²C-compatible two-wire interface, and hardware write protection via the WP pin. It delivers high reliability with 1 million write cycles and 40-year data retention, used in industrial control systems for parameter storage and calibration data backup.

For engineers reviewing the AT24C128B-PU datasheet, AT24C128B-PU pinout, AT24C128B-PU application, or AT24C128B-PU equivalent, this page provides verified package mapping (8-lead PDIP), confirmed pin functions (A0–A2, SDA, SCL, WP, VCC, GND), endurance and timing specs, and real-world use cases in embedded instrumentation and power management firmware.

Technical Context

The AT24C128B-PU implements a cascaded two-wire serial interface with Schmitt-triggered, noise-filtered inputs and open-drain SDA/SCL pins compatible with standard I²C bus protocols. Its internal address counter supports current-address, random-address, and sequential read modes, while the 64-byte page write buffer enables efficient bulk updates without external address management.

Device addressing uses three hardware-configurable pins (A0–A2) to support up to eight devices on a shared bus, with a fixed 7-bit base address (1010xxx). The WP pin provides hardware-level write inhibition when tied to VCC, and the EEPROM enters low-power standby mode after STOP condition detection or internal write completion.

Key Specifications

Pinout & Package

AT24C128B-PU is supplied in an 8-lead JEDEC-standard Plastic Dual Inline Package (PDIP), designated 8P3 per Microchip's ordering guide. Pin 1 is marked by a dot; leads are gull-wing shaped with 0.100" pitch and 0.300" body width.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT24C128C-PU, the AT24C128B-PU offers proven industrial reliability at lower cost but lacks extended temperature support; versus M24128-BWMN6TP, it provides broader 1.8 V operation and Atmel/Microchip's long-term supply commitment, though with distinct device addressing.

Availability

AT24C128B-PU is available at Aetrix Electronics and suitable for industrial automation, medical instrumentation, and smart metering applications requiring stable component supply, long-lifecycle support, and RoHS-compliant through-hole packaging.

Supply support for AT24C128B-PU 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 production, documentation, and technical support for the AT24C128B-PU family. The company specializes in microcontrollers, analog, and memory solutions for embedded markets.

The AT24C128B-PU belongs to Microchip's serial EEPROM product line, designed specifically for low-power, high-reliability nonvolatile storage in industrial, medical, and communications equipment where data integrity and long-term retention are critical.

FAQ

What is the maximum I²C clock frequency supported by the AT24C128B-PU at 1.8 V?

The AT24C128B-PU supports up to 400 kHz I²C clock frequency when operated at 1.8 V, as specified in Table 5-3 of the official datasheet. This limit ensures reliable signal integrity and noise immunity in low-voltage systems. At higher supply voltages (e.g., 5.5 V), the device supports 1 MHz operation. The AT24C128B-PU's internal timing logic enforces these limits automatically based on VCC level.

Does the AT24C128B-PU require external pull-up resistors on SDA and SCL lines?

Yes, the AT24C128B-PU requires external pull-up resistors on both SDA and SCL lines because its I²C interface uses open-drain outputs. Typical values range from 1.3 kΩ (for 5.5 V, 1 MHz) to 10 kΩ (for 1.8 V, 400 kHz), as defined in the AC characteristics section. Without proper pull-ups, the AT24C128B-PU cannot generate valid I²C START/STOP conditions or acknowledge addresses.

How many AT24C128B-PU devices can share the same I²C bus?

Up to eight AT24C128B-PU devices can share a single I²C bus, enabled by the three hardware address pins (A0, A1, A2). Each pin can be tied to VCC or GND, yielding 2³ = 8 unique 7-bit device addresses (1010xxx). The AT24C128B-PU's address scheme is backward-compatible with other AT24Cxx EEPROMs, allowing mixed-family bus configurations.

What happens if the WP pin on the AT24C128B-PU is left unconnected?

If the WP pin on the AT24C128B-PU is left floating, it is internally pulled down to GND, enabling normal write operations. However, Microchip explicitly recommends against this practice due to risk of capacitive coupling inducing false high states in noisy environments. For reliable operation, WP should be actively tied to either VCC (to disable writes) or GND (to enable writes); the AT24C128B-PU's behavior is deterministic only with a defined bias.

Is the AT24C128B-PU compatible with standard I²C protocol stacks in common microcontrollers?

Yes, the AT24C128B-PU is fully compatible with standard I²C protocol stacks in ARM Cortex-M, PIC, AVR, and ESP32 microcontrollers. It adheres to I²C specification timing (START/STOP, ACK/NACK, clock stretching) and uses standard 7-bit addressing with R/W bit. No custom drivers are needed - the AT24C128B-PU behaves identically to generic I²C EEPROMs in HAL libraries and RTOS middleware.