Renesas RM24C256DS-LSNI-B

Overview

RM24C256DS-LSNI-B from Adesto Technologies is a 256 Kbit 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 serves as a low-energy, high-endurance data storage element in space-constrained industrial sensor nodes and secure boot configurations.

For engineers reviewing the RM24C256DS-LSNI-B datasheet, RM24C256DS-LSNI-B pinout, RM24C256DS-LSNI-B application, or RM24C256DS-LSNI-B equivalent, key selection criteria include its 100,000 write cycles at full temperature range, 50 nJ byte-write energy, 1.5 ms page-write time, and dual-access capability for both main memory and factory/user OTP registers via distinct I²C control codes (1010 vs 1011).

Technical Context

The RM24C256DS-LSNI-B implements a slave-only I²C interface with SDA (open-drain) and SCL (input-only), supporting standard-mode (100 kHz), fast-mode (400 kHz), and fast-mode plus (1 MHz) clock rates. Its internal address pointer is shared between main EEPROM array (A0–A14 valid) and 128-byte OTP register space, with upper address bits masked during OTP access.

Write operations are initiated by STOP condition after address and data transmission; WP pin state sampled at STOP determines write enable/disable. Acknowledge polling - sending repeated control bytes until SDA low is returned - is used to detect write completion, as the device suspends ACK during internal write cycles.

Key Specifications

Pinout & Package

RM24C256DS-LSNI-B is packaged in an 8-lead SOIC (Small Outline Integrated Circuit) with standard pin pitch and footprint. This package supports automated PCB assembly and provides thermal and mechanical reliability for industrial environments.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT24C256C-SSHL-T and M95256-DFMN6TP, RM24C256DS-LSNI-B delivers superior write energy efficiency (50 nJ vs ~500 nJ), guaranteed endurance across full industrial temperature range, and built-in hardware addressing - eliminating software overhead and enabling denser multi-device I²C networks.

Availability

RM24C256DS-LSNI-B is available at Aetrix Electronics and suitable for industrial sensor nodes, secure boot loaders, smart metering systems, and medical diagnostics equipment requiring stable component supply and long-term lifecycle support.

Supply support for RM24C256DS-LSNI-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 resource-constrained edge devices.

The RM24C256DS-LSNI-B belongs to Adesto's CBRAM®-based serial EEPROM product line, engineered for applications demanding extreme write endurance, minimal energy per operation, and integrated security features in compact industrial and medical systems.

FAQ

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

The RM24C256DS-LSNI-B supports I²C clock frequencies up to 1 MHz under recommended operating conditions (VCC = 1.65 V to 3.6 V, TA = −40°C to +85°C). This fast-mode plus capability allows high-speed configuration loading and reduces firmware update time compared to standard 100 kHz EEPROMs. The device maintains full timing compliance including tSCLH ≥ 500 ns and input rise/fall times within specification limits.

Does RM24C256DS-LSNI-B require external pull-up resistors on SDA and SCL lines?

Yes, RM24C256DS-LSNI-B requires external pull-up resistors on both SDA and SCL lines because SDA is open-drain and SCL is input-only. Recommended values are 10 kΩ for 100 kHz operation and 2 kΩ for 400 kHz or 1 MHz modes to meet rise time requirements (tRI ≤ 300 ns). Pull-up to VCC is mandatory; floating or weak pull-ups will cause communication failure or intermittent ACK loss.

How does the WP pin function during write operations in RM24C256DS-LSNI-B?

The WP pin in RM24C256DS-LSNI-B is sampled only at the STOP condition of each write command. When pulled high to VCC, it inhibits all write operations (byte, page, and OTP) while permitting unrestricted reads. When pulled low to GND, writes are enabled. Critically, toggling WP during an active write cycle has no effect - the decision is latched at STOP, ensuring deterministic behavior in noisy industrial environments.

Can RM24C256DS-LSNI-B be used alongside other I²C devices sharing the same bus?

Yes, RM24C256DS-LSNI-B supports multi-drop I²C bus configurations via its three hardware address pins (E0, E1, E2), allowing up to eight identical devices on one bus. Each device responds only when its E2:E1:E0 combination matches the corresponding bits in the master's control byte (1010b for memory, 1011b for OTP). No software address assignment or external multiplexing is required, simplifying scalable sensor node designs.

What distinguishes the OTP Security Register from main memory in RM24C256DS-LSNI-B?

The OTP Security Register in RM24C256DS-LSNI-B is a dedicated 128-byte space (64 factory-programmed, 64 user-programmable) accessed via I²C control code 1011b instead of 1010b. Unlike main memory, OTP writes are irreversible - once programmed, no further writes are possible. Addressing uses only lower 7 bits (masking upper 9), and the same internal address pointer is shared, requiring careful coordination between memory and OTP access sequences.