Microchip Technology 48L256T-I/SN

Overview

48L256T-I/SN from Microchip Technology Inc. is a 256-Kbit SPI serial EERAM integrating a 32,768 × 8-bit SRAM core with cell-based EEPROM backup, operating at up to 66 MHz over a 2.7V–3.6V supply, with automatic power-loss data retention and industrial temperature support (−40°C to +85°C). It serves as a drop-in nonvolatile SRAM replacement in embedded control, metering, and IoT edge nodes where data persistence without external backup circuitry is required.

For engineers reviewing the 48L256T-I/SN datasheet, 48L256T-I/SN pinout, 48L256T-I/SN application, or 48L256T-I/SN equivalent, key selection considerations include its symmetrical read/write timing, VCAP-supported autonomous store/recall behavior, HOLD pin suspend capability, STATUS register configurability, and compatibility with SPI Modes 0/3 in resource-constrained systems.

Technical Context

The 48L256T-I/SN implements a dual-memory architecture: a volatile 32K × 8 SRAM array accessible via standard SPI commands (READ/WRITE), and a hidden, cell-mirrored EEPROM array that operates transparently during VCC disruption. Its internal VCC monitor triggers automatic SRAM→EEPROM transfer when voltage drops below 2.30–2.65 V, using energy stored in the external 22–50 μF VCAP capacitor.

It supports SPI Modes 0 and 3 with MSb-first framing, uses a 16-bit address space, includes a writable 8-bit STATUS register (with BP1/BP0 block protection, ASE auto-store enable, PRO page rollover control), and provides dedicated opcodes for secure CRC-protected transfers, nonvolatile user space (2 bytes), and hibernate mode-enabling deterministic low-power operation without host intervention.

Key Specifications

Pinout & Package

8-Lead SOIC (Small Outline Integrated Circuit) package, 150 mil width, surface-mount, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 48L256T-I/SN, the 48L256T-I/MS offers identical functionality in a smaller footprint but requires layout revision, while the FM25V20A-G eliminates VCAP and offers infinite write cycles at the cost of lower speed and reduced data retention (10 years vs. 100 years).

Availability

48L256T-I/SN is available at Aetrix Electronics and suitable for smart metering, industrial PLC data logging, medical calibration storage, automotive telematics buffering, and IoT edge node configuration retention requiring stable component supply across multi-year production cycles.

Supply support for 48L256T-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, FPGA, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 48L256T-I/SN belongs to Microchip's EERAM product line, engineered specifically to replace battery-backed SRAM and discrete EEPROM+SRAM combinations in applications demanding seamless, autonomous nonvolatile data retention without firmware complexity.

FAQ

What is the function of the VCAP pin on the 48L256T-I/SN?

VCAP (pin 3) connects to an external 22–50 μF capacitor that stores energy used exclusively for autonomous SRAM-to-EEPROM backup during VCC drop. The 48L256T-I/SN monitors VCC and, upon detecting a fall below 2.30–2.65 V, isolates VCC and powers the store operation from VCAP - ensuring data preservation without host involvement. This capacitor must be rated ≥6.3V and placed close to the 48L256T-I/SN.

Does the 48L256T-I/SN require a Write Enable command before every SRAM write?

Yes, the 48L256T-I/SN requires execution of the WREN (06h) opcode to set the Write Enable Latch (WEL) bit before each WRITE or WRSR command. The WEL bit resets to '0' after any write completes, power-up, or WRDI instruction. Without WREN, the 48L256T-I/SN ignores WRITE opcodes and remains in standby - a hardware-level protection against accidental overwrites.

How does the HOLD pin affect ongoing operations in the 48L256T-I/SN?

The HOLD pin suspends SPI communication mid-sequence without resetting the internal state: SO immediately goes high-Z, and SI/SCK transitions are ignored until HOLD is deasserted. However, HOLD does not pause active internal operations - if a STORE or RECALL is in progress, it continues uninterrupted. To use HOLD correctly, assert/deassert it only while SCK is low; otherwise, activation/resumption delays until the next SCK low pulse.

Can the 48L256T-I/SN be used with SPI Mode 1 or Mode 2?

No, the 48L256T-I/SN supports only SPI Modes 0 and 3 - defined by data sampled on the rising SCK edge and output on the falling edge. Mode 0 uses low-idle SCK; Mode 3 uses high-idle SCK. Modes 1 and 2 (sampling on falling edge) are incompatible and will cause communication failure. The 48L256T-I/SN's timing diagrams and functional description explicitly exclude them.

What is the purpose of the nonvolatile user space in the 48L256T-I/SN?

The 48L256T-I/SN includes a dedicated 2-byte nonvolatile user space, separate from the main SRAM array, accessible via WRNUR/C2h and RDNUR/C3h opcodes. It stores infrequently changed system identifiers (e.g., serial numbers, calibration constants) and is copied to nonvolatile memory alongside SRAM and STATUS register during AutoStore or Software Store - enabling persistent, address-free configuration storage independent of main memory access patterns.