Microchip Technology 25LC256-I/P

Overview

25LC256-I/P from Microchip Technology Inc. is a 256 Kbit (32,768 × 8) SPI bus serial EEPROM with 64-byte page write capability, 10 MHz max clock frequency, and industrial temperature range (−40°C to +85°C). It features hardware write protection via WP pin, HOLD functionality for interrupt-safe bus suspension, and operates from 2.5V to 5.5V supply. It is commonly used in embedded systems for firmware parameter storage, calibration data retention, and configuration backup.

For engineers reviewing the 25LC256-I/P datasheet, 25LC256-I/P pinout, 25LC256-I/P application, or 25LC256-I/P equivalent, key selection criteria include VCC range compatibility (2.5–5.5V), 64-byte page boundary handling, WPEN-controlled hardware write protection, and HOLD timing constraints (THS/THH ≤ 80 ns at 1.8V).

Technical Context

The 25LC256-I/P implements a standard SPI Mode 0,0 interface (CPOL = 0, CPHA = 0) with separate SI and SO lines, requiring CS assertion for device selection and SCK synchronization. Its internal architecture includes an 8-bit instruction register, status register with WIP/WEL/BP bits, and page latches enabling up to 64 bytes per write cycle.

Write operations require explicit WREN instruction followed by CS high-to-low transition to initiate TWC (≤5 ms); read operations support sequential addressing with automatic address rollover at 0x7FFF. Built-in power-on reset clears the write enable latch, and WP pin functionality is gated by the nonvolatile WPEN bit in the STATUS register.

Key Specifications

Pinout & Package

25LC256-I/P is packaged in an 8-lead PDIP (Plastic Dual In-Line Package) with 300-mil body width, lead pitch of 0.100", and through-hole mounting. Pin 1 is marked with a notch or dot; orientation follows standard DIP convention with pin 1 at top-left when notch faces up.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 25AA256-I/P, the 25LC256-I/P offers tighter VCC lower limit (2.5V vs. 1.8V) but identical timing, protection, and endurance - making it optimal for legacy 5V/3.3V industrial systems. Versus AT25DF256A-SSH-T, it provides deterministic write latency, simpler command protocol, and robust hardware write disable - critical for safety-critical parameter storage.

Availability

25LC256-I/P is available at Aetrix Electronics and suitable for industrial PLCs, automotive ECUs, medical infusion devices, and smart metering systems requiring stable component supply across long product lifecycles.

Supply support for 25LC256-I/P 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 microcontroller, analog, and Flash-IP solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The 25LC256 belongs to Microchip's serial EEPROM product line, engineered for reliable, low-power nonvolatile data storage in resource-constrained embedded systems where deterministic write behavior and long-term data integrity are essential.

FAQ

What is the maximum clock frequency supported by the 25LC256-I/P?

The 25LC256-I/P supports up to 10 MHz clock frequency when VCC is 4.5V to 5.5V. At 2.5V ≤ VCC < 4.5V, the maximum clock drops to 5 MHz, and at 1.8V ≤ VCC < 2.5V it is 3 MHz. These limits are defined in Table 1-2 AC Characteristics and must be respected to ensure reliable SI sampling and SO timing compliance. The 25LC256-I/P datasheet specifies these derated frequencies to maintain setup/hold margins across voltage and temperature ranges.

Does the 25LC256-I/P require external pull-up resistors on its SPI lines?

The 25LC256-I/P SO pin is open-drain and requires an external pull-up resistor (typically 4.7 kΩ) to VCC for proper logic-high signaling. CS, SI, SCK, WP, and HOLD inputs are CMOS-compatible and do not require pull-ups unless needed for system-level noise immunity or default state assurance. The 25LC256-I/P internal input leakage current is ±1 µA, so weak pull-ups (≥10 kΩ) may suffice for floating-input prevention in low-noise environments.

How does the HOLD function operate in the 25LC256-I/P during an active SPI transaction?

The HOLD function in the 25LC256-I/P suspends an ongoing SPI sequence when HOLD is pulled low while SCK is low; all inputs except CS are ignored, and SO enters high-impedance. To resume, HOLD must be raised while SCK remains low - then communication continues from the exact bit position where it paused. This behavior is confirmed in Figure 1-1 and Section 2.1 of the 25LC256-I/P datasheet, enabling interrupt servicing without retransmission overhead.

Can the 25LC256-I/P be used in automotive applications?

Yes, the 25LC256-I/P is AEC-Q100 qualified for automotive applications and rated for the extended temperature range (−40°C to +125°C) in appropriate package variants. However, the specific 25LC256-I/P variant uses the Industrial (I) temperature grade (−40°C to +85°C) and PDIP package, which is not automotive-qualified. For automotive use, select 25LC256-E/P or surface-mount variants like 25LC256-E/SN that carry the AEC-Q100 qualification mark and extended temp rating.

What happens if a page write crosses a 64-byte boundary in the 25LC256-I/P?

If a page write command attempts to cross a 64-byte boundary (e.g., writing bytes starting at address 0x003E), the 25LC256-I/P wraps the data to the start of the same page (0x0000), overwriting previously written bytes in that page. This behavior is explicitly documented in Section 2.3 and Note under "Page write operations" - firmware must validate address alignment and split writes across page boundaries to avoid unintended data corruption in the 25LC256-I/P.