Renesas RM24C256DS-LTAI-B

Overview

RM24C256DS-LTAI-B from Adesto Technologies is a 256Kbit non-volatile serial EEPROM IC using CBRAM® resistive memory technology, operating from 1.65V to 3.6V with I²C interface up to 1 MHz, 64-byte page size, and integrated 128-byte OTP security register. It delivers ultra-low-energy byte writes (50 nJ), 100,000 write cycles, and >40-year data retention at 125°C for secure embedded firmware storage.

For engineers reviewing the RM24C256DS-LTAI-B datasheet, RM24C256DS-LTAI-B pinout, RM24C256DS-LTAI-B application, or RM24C256DS-LTAI-B equivalent, key selection criteria include I²C bus speed support (100 kHz/400 kHz/1 MHz), write-protect functionality via WP pin, external device addressing via E0–E2 pins, OTP security register partitioning (64B factory ID + 64B user-programmable), and CBRAM-specific endurance advantages over floating-gate EEPROMs.

Technical Context

This device implements a slave-only 2-wire I²C interface with SDA (open-drain bidirectional) and SCL (input-only), supporting standard, fast, and high-speed modes up to 1 MHz. Device selection uses three hardware address bits (E0, E1, E2) enabling up to eight devices on one bus.

It integrates dual memory spaces: a 256Kbit main EEPROM array (32,768 × 8-bit) and a 128-byte OTP Security Register with separate control code (1011b vs. 1010b for main array). Addressing uses a shared internal pointer, and both arrays support random/sequential read, byte write, and 64-byte page write with identical timing (1.5 ms page write, 60 µs byte write).

Key Specifications

Pinout & Package

RM24C256DS-LTAI-B is packaged in an 8-lead TSSOP (Thin Shrink Small Outline Package) with 0.65 mm lead pitch, RoHS-compliant and halogen-free.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT24C256C-SSHL-T and BR24G256FJ-WE2, RM24C256DS-LTAI-B uniquely combines 125°C data retention, CBRAM-based temperature-invariant endurance, and integrated OTP security - making it the only option among the three for safety-critical, high-reliability, and cryptographically secured applications.

Availability

RM24C256DS-LTAI-B is available at Aetrix Electronics and suitable for industrial sensor calibration, secure IoT identity management, medical device configuration, automotive BCM programming, and high-reliability embedded systems requiring stable component supply and long-term lifecycle support.

Supply support for RM24C256DS-LTAI-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

Adesto Technologies (acquired by Dialog Semiconductor in 2020, now part of Renesas Electronics) specialized in ultra-low-power, high-reliability non-volatile memory solutions for constrained embedded systems.

The RM24C256DS-LTAI-B belongs to Adesto's CBRAM®-based serial EEPROM product line, designed specifically for applications demanding superior endurance, low-energy writes, and integrated security features in harsh thermal environments.

FAQ

What is the maximum I²C clock frequency supported by RM24C256DS-LTAI-B?

The RM24C256DS-LTAI-B supports I²C clock frequencies up to 1 MHz across its full operating voltage range (1.65 V to 3.6 V) and temperature range (−40°C to +85°C). This enables faster configuration loading and firmware parameter updates compared to standard 400 kHz EEPROMs. The device maintains full AC timing compliance-including tSCLH ≥ 500 ns and input rise/fall times-ensuring robust communication in noise-prone industrial environments. RM24C256DS-LTAI-B achieves this without requiring external speed-grade qualification.

How does the OTP Security Register in RM24C256DS-LTAI-B function, and what happens after programming?

The RM24C256DS-LTAI-B includes a 128-byte OTP Security Register divided into two 64-byte sections: factory-programmed unique identifier (read-only) and user-programmable space (write-once). Programming uses I²C control code 1011b and follows page-write protocol. Once any byte in the user section is written, the entire 64-byte block is permanently locked - no further writes are possible. RM24C256DS-LTAI-B enforces this at the silicon level; subsequent write attempts return acknowledgment but have no effect. This ensures cryptographic key immutability essential for secure boot and device authentication.

Can RM24C256DS-LTAI-B operate reliably at 1.65 V supply voltage?

Yes, RM24C256DS-LTAI-B is fully specified and tested for operation at 1.65 V minimum supply voltage across −40°C to +85°C. All key parameters-including 1 MHz I²C timing, 60 µs byte write, 1.5 ms page write, and 0.25 mA active read current-are guaranteed at VCC = 1.65 V. This allows direct integration with 1.8 V microcontrollers and ultra-low-power SoCs without level-shifting circuitry. RM24C256DS-LTAI-B maintains full functionality and endurance rating even at this minimum rail, unlike many competing EEPROMs that derate performance below 2.5 V.

What is the purpose of the E0, E1, and E2 pins on RM24C256DS-LTAI-B, and how do they affect I²C addressing?

The E0, E1, and E2 pins on RM24C256DS-LTAI-B are hardware-configurable address bits that determine the device's 7-bit I²C slave address. They correspond to the three least-significant bits of the control byte (1010xxx for main memory access). By setting each pin to VCC or GND, users select one of eight unique addresses (1010000b to 1010111b), enabling up to eight RM24C256DS-LTAI-B devices on a single I²C bus without software address management. RM24C256DS-LTAI-B compares these pin states against incoming control byte bits during START condition to determine selection - no external address decoding logic is required.

Does RM24C256DS-LTAI-B require external pull-up resistors on SDA and SCL, and what values are recommended?

Yes, RM24C256DS-LTAI-B requires external pull-up resistors on both SDA and SCL because its SDA pin is open-drain and SCL is input-only. Recommended values are 2 kΩ for 1 MHz operation (to meet 100 ns fall time requirement), 4.7 kΩ for 400 kHz, and 10 kΩ for 100 kHz. These values ensure proper signal rise/fall times while minimizing bus contention current. RM24C256DS-LTAI-B specifies maximum bus capacitance of 400 pF; exceeding this may require lower pull-up resistance or bus buffering. Pull-ups must connect to the same VCC rail used by the device.