NXP Semiconductors PCA24S08AD

Overview

The PCA24S08AD from NXP Semiconductors is a 1024 × 8-bit (8 kbit) I²C-compatible serial EEPROM with hardware-based access protection, organized into eight 128-byte blocks and supporting byte/page write modes. It operates from 2.5 V to 3.6 V, features 100,000 write cycles per byte, and delivers 10-year data retention. It is used in embedded systems requiring secure, non-volatile parameter storage-such as industrial controllers, medical devices, and smart meters.

For engineers reviewing the PCA24S08AD datasheet, PCA24S08AD pinout, PCA24S08AD application, or PCA24S08AD equivalent, key selection considerations include its SO8 package, block- and page-level write protection via dedicated PROT/WP pins, I²C clock support up to 400 kHz, and compatibility with legacy 24C08 designs while extending security functionality.

Technical Context

The PCA24S08AD implements an I²C-bus interface with slave address range A8h–AFh (R/W bit included), where B2/B1 bits select memory blocks and internal addressing supports auto-incremented sequential reads and page-aligned writes. Its access protection logic uses dedicated APP and ID pages accessed via device codes B8h/B9h, with sticky bits (SB0–SB7, SBAP) enforcing irreversible lock-down of protection registers.

Write operations require WP = LOW and are self-timed (<5 ms), while the PROT pin serves as a power-good reset signal that sets all sticky bits HIGH on assertion. The device enforces strict boundary handling: multi-byte reads wrap within blocks, and page writes are limited to 16 bytes with no cross-page auto-increment-exceeding this triggers NACK and ignores overflow data.

Key Specifications

Pinout & Package

PCA24S08AD is supplied in an SO8 package (SOT96-1): plastic small outline, 8 leads, 3.9 mm body width, with pins 1 and 2 not connected, and pin 3 serving as active-low PROT reset input.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT24C08C-PU and M95M01-RMN6TP, the PCA24S08AD uniquely delivers hardware-enforced, granular memory access control within an I²C-compatible 8-kbit footprint-enabling secure parameter management without MCU-side encryption overhead or protocol conversion.

Availability

PCA24S08AD is available at Aetrix Electronics and suitable for industrial control systems, medical diagnostics equipment, smart energy meters, and automotive body electronics requiring stable component supply and long-term lifecycle support.

Supply support for PCA24S08AD 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

NXP Semiconductors is a global semiconductor company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and IoT applications.

The PCA24S08AD belongs to NXP's serial EEPROM product line, designed specifically for applications demanding hardware-level memory protection, I²C interoperability, and extended reliability in harsh operating environments.

FAQ

What is the primary function of the PROT pin on the PCA24S08AD?

The PROT pin on the PCA24S08AD is an active-low reset input that places the serial interface in reset and sets all sticky bits (SB0–SB7, SBAP) to logic HIGH when asserted. This enables reconfiguration of locked access protection registers after power-up or fault recovery. The PCA24S08AD requires PROT to be HIGH for normal I²C communication, and its state directly governs whether protection register writes are permitted.

How does the PCA24S08AD implement memory access protection?

The PCA24S08AD implements memory access protection through dedicated Access Protection Page (APP) and ID Page stored at device addresses B8h/B9h. Each of the eight 128-byte blocks has programmable protection bits (PB0–PB7) and corresponding sticky bits (SB0–SB7) that, once cleared, permanently lock protection settings. The PCA24S08AD also supports individual page write protection (WPN bits) for Block 0 and full-array hardware write disable via the WP pin.

Can the PCA24S08AD be used as a direct replacement for standard 24C08 EEPROMs?

The PCA24S08AD is pin-compatible with standard 24C08 devices except for pins 1, 2, and 3-where it substitutes n.c./n.c./PROT instead of A0/A1/A2. Functionally, it maintains full I²C protocol compatibility but adds access protection, APP/ID pages, and PROT/WP control. The PCA24S08AD requires minor firmware adaptation to leverage security features but operates identically in basic read/write mode.

What are the timing constraints for page writes on the PCA24S08AD?

Page writes on the PCA24S08AD are limited to exactly 16 bytes aligned to internal 16-byte boundaries. The device acknowledges each byte but ignores data beyond the 16th byte if a STOP condition is delayed-causing corruption of overlapping locations. The PCA24S08AD completes internal write cycles in under 5 ms, during which it does not acknowledge I²C addresses until completion.

Does the PCA24S08AD support multi-byte reads across block boundaries?

No, the PCA24S08AD does not support multi-byte reads across block boundaries. When a sequential read reaches the end of a 128-byte block, the internal address counter wraps to the start of that same block-not the next block. This behavior differs from generic EEPROMs and must be accounted for in host firmware to avoid unintended data repetition. The PCA24S08AD enforces this boundary strictly per its functional specification.