Microchip Technology 48L256-I/SN

Overview

48L256-I/SN from Microchip Technology Inc. is a 256-Kbit serial EERAM integrating a 32,768 × 8-bit SRAM core with cell-based hidden EEPROM backup, SPI interface (up to 66 MHz), and automatic power-loss data retention. It operates at 2.7V–3.6V over –40°C to +85°C and delivers 5 mA active current, enabling nonvolatile SRAM behavior in industrial control logging and real-time parameter storage.

For engineers reviewing the 48L256-I/SN datasheet, 48L256-I/SN pinout, 48L256-I/SN application, or 48L256-I/SN equivalent, key selection considerations include VCAP capacitor support (22–50 μF), AutoStore trip voltage (2.30–2.65 V), Hibernate current (3 μA), STATUS register write-protection control, and SPI Mode 0/3 compatibility for deterministic timing in resource-constrained embedded systems.

Technical Context

The 48L256-I/SN implements a dual-memory architecture where SRAM provides symmetrical read/write access while EEPROM backup occurs transparently on VCC drop below 2.30–2.65 V. Its internal VCC monitor triggers parallel SRAM-to-EEPROM transfer using energy stored in the external VCAP capacitor (33 μF typical), eliminating software intervention.

SPI communication uses Mode 0 or Mode 3 only, with data latched on SCK rising edge and output on falling edge. The HOLD pin enables mid-sequence pause without clock reset, and the STATUS register includes volatile WEL and RDY/BSY bits plus nonvolatile BP[1:0] block protection and ASE AutoStore enable control.

Key Specifications

Pinout & Package

48L256-I/SN is housed in an 8-Lead SOIC package (SOIC-8, 150 mil width), with gull-wing leads, JEDEC MS-012AC compliant footprint, and moisture sensitivity level (MSL) 3 per J-STD-020.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 48L64-I/SN, the 48L256-I/SN offers 4× memory headroom for firmware expansion and complex state tracking; versus FM25V05-G, it delivers lower hibernate current and integrated hardware write protection-critical for certified industrial and medical deployments.

Availability

48L256-I/SN is available at Aetrix Electronics and suitable for industrial control logging, medical device parameter storage, automotive body control modules, and smart meter firmware configuration requiring stable component supply across extended product lifecycles.

Supply support for 48L256-I/SN 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 Inc. is a leading provider of microcontrollers, analog components, and memory solutions, headquartered in Chandler, Arizona, with global manufacturing and support infrastructure.

The 48L256-I/SN belongs to Microchip's EERAM product line, designed specifically to replace battery-backed SRAM and simplify nonvolatile data retention in space- and power-constrained embedded systems.

FAQ

What is the purpose of the VCAP pin on the 48L256-I/SN?

VCAP (Pin 3) connects to an external 22–50 μF capacitor that stores energy used to power the 48L256-I/SN during VCC collapse. When system voltage drops below 2.30–2.65 V, the 48L256-I/SN uses this stored charge to execute a full SRAM-to-EEPROM transfer, ensuring zero-data-loss power fail recovery. The capacitor must be rated ≥6.3 V and placed as close as possible to Pin 3 and VSS.

Does the 48L256-I/SN require a write-enable command before every SRAM write?

Yes, the 48L256-I/SN requires the WREN (06h) instruction to set the Write Enable Latch (WEL) bit before each WRITE or WRSR command. The WEL bit resets to '0' automatically after any write completes, on power-up, or when WRDI (04h) is issued. This prevents accidental writes and enforces explicit enablement per operation, enhancing system reliability in noisy environments.

How does the HOLD function operate on the 48L256-I/SN during an active SPI transaction?

The HOLD pin on the 48L256-I/SN suspends SPI communication mid-sequence without resetting internal state. To activate HOLD, the pin must be driven low while SCK is low; SO immediately enters high-Z, and SI/SCK transitions are ignored. Resuming requires driving HOLD high while SCK is low. HOLD has no effect on ongoing internal store/recall operations, which continue uninterrupted.

Can the 48L256-I/SN be used with SPI Mode 1 or Mode 2?

No, the 48L256-I/SN supports only SPI Modes 0 and 3. In both modes, data is sampled on the SCK rising edge and output on the falling edge. Mode 0 uses idle-low SCK; Mode 3 uses idle-high SCK. Using Mode 1 or Mode 2 will result in incorrect data sampling or communication failure because the 48L256-I/SN's internal timing logic is hardwired for these two specific phase/polarity combinations.

What is the function of the 16-bit nonvolatile user space in the 48L256-I/SN?

The 48L256-I/SN includes a dedicated 16-bit (2-byte) nonvolatile user space accessible via WRNUR (C2h) and RDNUR (C3h) commands. It stores user-defined metadata such as calibration constants or firmware revision IDs. Like the main SRAM array, its contents are automatically backed up to EEPROM during power loss or software STORE, ensuring end-to-end persistence without additional software management overhead.