Microchip Technology AT24C128B-TH-B

Overview

AT24C128B-TH-B from Microchip Technology (formerly Atmel) is a 128 Kbit (16,384 × 8) two-wire serial EEPROM with 1.8 V to 5.5 V operation, 64-byte page write capability, and hardware write protection via the WP pin. It supports up to 1 MHz I²C communication at 5.5 V and 400 kHz at 1.8 V, and is qualified for industrial temperature range (−40°C to +85°C). It is commonly used in embedded systems for parameter storage, calibration data retention, and firmware configuration in smart meters and industrial controllers.

For engineers reviewing the AT24C128B-TH-B datasheet, AT24C128B-TH-B pinout, AT24C128B-TH-B application, or AT24C128B-TH-B equivalent, key selection considerations include its TSSOP-8 package (8A2), NiPdAu lead finish, 1.8–5.5 V supply compatibility, 40-year data retention, and 1 million write endurance - critical for long-life, low-power, field-deployed devices requiring robust nonvolatile memory.

Technical Context

The AT24C128B-TH-B implements a standard I²C-compatible two-wire interface with Schmitt-triggered, noise-filtered SDA and SCL inputs. Its internal architecture features a 14-bit address counter supporting random and sequential reads, and a page-based write engine enabling partial-page writes within 64-byte boundaries.

Device addressing uses three hardware-configurable pins (A0–A2), allowing up to eight AT24C128B-TH-B units on a shared bus. The WP pin provides hardware-level write inhibition when tied to VCC, complementing software-controlled write protection for secure configuration storage in safety-critical subsystems.

Key Specifications

Pinout & Package

AT24C128B-TH-B is supplied in an 8-lead Thin Shrink Small Outline Package (TSSOP), JEDEC MO-153 compliant, with 0.65 mm pitch and NiPdAu lead finish. The package measures 3.0 mm × 4.4 mm × 1.2 mm (max height) and is optimized for thermal performance and reflow compatibility.

Key Features

Applications

Equivalent & Alternatives

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

Compared with M24128-BWMN6TP and R1EX24128ASAS0I, the AT24C128B-TH-B delivers broader voltage-speed coverage (400 kHz @ 1.8 V, 1 MHz @ 5.5 V), integrated address pin pull-downs, and industry-leading 40-year data retention - making it optimal for mixed-voltage industrial designs requiring minimal external components and maximum long-term reliability.

Availability

AT24C128B-TH-B is available at Aetrix Electronics and suitable for smart metering, industrial PLCs, medical diagnostics, and automotive body control modules requiring stable component supply across extended product lifecycles.

Supply support for AT24C128B-TH-B 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 continues to manufacture, qualify, and support the AT24Cxx family of serial EEPROMs with full backward compatibility and long-term product roadmaps.

The AT24C128B-TH-B belongs to Microchip's industrial-grade serial EEPROM product line, designed specifically for robust, low-power, nonvolatile data storage in harsh environments where extended temperature operation, high endurance, and long data retention are mandatory.

FAQ

What is the maximum I²C clock frequency supported by the AT24C128B-TH-B?

The AT24C128B-TH-B supports up to 1 MHz I²C clock frequency when VCC is 5.5 V, and 400 kHz when operating at 1.8 V. These speeds are specified under industrial temperature conditions (−40°C to +85°C) with appropriate pull-up resistors and bus capacitance ≤100 pF. The device does not support high-speed mode (3.4 MHz) or ultra-fast mode.

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

Yes, the AT24C128B-TH-B requires external pull-up resistors on both SDA and SCL lines because its I²C interface uses open-drain outputs. Typical values range from 2.2 kΩ to 10 kΩ depending on bus capacitance and desired rise time; Microchip recommends 4.7 kΩ for standard-mode (100 kHz) and 2.2 kΩ for fast-mode (400 kHz/1 MHz) operation with ≤400 pF total bus load.

How is the device address configured on the AT24C128B-TH-B?

The AT24C128B-TH-B uses three hardware address pins - A0, A1, and A2 - each tied to either VCC or GND to set a unique 3-bit device address. This allows up to eight AT24C128B-TH-B devices on a single I²C bus. Floating A0–A2 pins are internally pulled down, but Microchip strongly recommends hardwiring them to avoid noise-induced addressing errors in industrial environments.

What is the purpose of the WP pin on the AT24C128B-TH-B?

The WP (Write Protect) pin on the AT24C128B-TH-B provides hardware-level inhibition of all write operations when connected to VCC. When WP is grounded, normal read and write functions operate. This feature prevents accidental or malicious overwrites of critical calibration data, security keys, or configuration registers - especially valuable during firmware updates or field service operations.

Is the AT24C128B-TH-B compatible with 1.8 V microcontrollers?

Yes, the AT24C128B-TH-B is fully compatible with 1.8 V microcontrollers: it operates from 1.8 V to 5.5 V, supports 400 kHz I²C communication at 1.8 V, and features Schmitt-triggered inputs that ensure reliable signal recognition even with marginal noise margins. Its 1.8 V logic threshold (VIH ≥ 0.7×VCC = 1.26 V) aligns with standard 1.8 V GPIO specifications.