Microchip Technology AT25040B-XHL-T

Overview

AT25040B-XHL-T from Microchip Technology is a 4 Kbit (512 × 8) SPI Serial EEPROM with industrial-grade operation (−40°C to +85°C), 1.8V–5.5V supply range, and 20 MHz max clock rate at 5V. It features hardware/software write protection, 8-byte page write mode, and self-timed write cycles ≤5 ms - deployed in embedded systems for firmware parameter storage, calibration data retention, and configuration backup.

For engineers reviewing the AT25040B-XHL-T datasheet, AT25040B-XHL-T pinout, AT25040B-XHL-T application, or AT25040B-XHL-T equivalent, key selection considerations include SPI Mode 0/3 compatibility, VCC voltage scaling across 1.8–5.5V, block-level write protection (1/4, 1/2, or full array), HOLD/CS timing coordination, and 1M-cycle endurance with 100-year data retention.

Technical Context

The AT25040B-XHL-T implements a synchronous SPI slave interface with fixed MSB-first serial framing, supporting both Mode 0 (SCK idle low) and Mode 3 (SCK idle high). Its internal architecture includes a dedicated STATUS register (BP1/BP0 for block protection, WEL for write enable, RDY/BSY for cycle status) and high-voltage generation circuitry enabling byte/page writes without external programming voltage.

Write operations are controlled via explicit opcodes (WREN, WRITE, WRSR) and validated by polling the RDY/BSY bit. The HOLD pin suspends serial input while preserving internal state, and the WP pin provides hardware-level inhibition of all write commands when driven low - both pins operate independently of CS assertion timing and do not affect ongoing internal write cycles.

Key Specifications

Pinout & Package

AT25040B-XHL-T is packaged in an 8-lead TSSOP (Thin Shrink Small Outline Package) with standard 0.65 mm lead pitch and exposed pad (GND-connected or floating per design).

Key Features

Applications

Equivalent & Alternatives

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

Compared with M95040-DRMN6TP/K, AT25040B-XHL-T delivers guaranteed industrial temperature operation and HOLD functionality; versus CAT25040VI-GT3, it requires STATUS register configuration adjustment due to differing BP bit ordering despite identical protection granularity and timing.

Availability

AT25040B-XHL-T is available at Aetrix Electronics and suitable for industrial sensor calibration storage, medical device configuration backup, and automotive body control module applications requiring stable component supply, long-lifecycle assurance, and RoHS-compliant packaging.

Supply support for AT25040B-XHL-T 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, FPGA, and memory solutions, with global manufacturing and quality certifications including ISO 9001 and IATF 16949.

The AT25040B-XHL-T belongs to Microchip's AT25xxx-B series of SPI Serial EEPROMs, designed specifically for reliable, low-power nonvolatile storage in space-constrained industrial and automotive systems where voltage flexibility and data integrity are critical.

FAQ

What is the maximum SPI clock frequency supported by the AT25040B-XHL-T at 3.3V operation?

The AT25040B-XHL-T supports up to 10 MHz SPI clock frequency when VCC is between 2.5V and 5.5V - covering standard 3.3V operation. This is specified in Table 4-3 of the DS20006251A datasheet under AC Characteristics. At 3.3V, timing parameters such as tWH (SCK high time) and tSU (data setup time) are relaxed to ensure robust signal integrity without requiring special PCB layout techniques.

Does the AT25040B-XHL-T require an external pull-up resistor on the CS pin?

Yes, the AT25040B-XHL-T datasheet recommends connecting the CS pin to VCC via a pull-up resistor ≤10 kΩ to ensure robust power-up behavior. This prevents spurious selection during VCC ramp-up and guarantees the device enters Standby mode correctly. The recommendation appears in Section 2.1 "Chip Select (CS)" of DS20006251A, noting that CS should follow VCC upon power-up.

How does the HOLD pin function during an active write cycle in the AT25040B-XHL-T?

The HOLD pin has no effect on an ongoing internal write cycle in the AT25040B-XHL-T. As stated in Section 5.3, "Hold Function", HOLD only suspends serial communication - it does not pause or abort the self-timed 5 ms write operation once initiated. During a write, SO remains high-Z and SI/SCK are ignored, but the internal EEPROM programming proceeds to completion regardless of HOLD state.

Can the AT25040B-XHL-T be used with SPI Mode 1 or Mode 2 interfaces?

No, the AT25040B-XHL-T explicitly supports only SPI Modes 0 and 3, as confirmed in the Features section and Section 5.1 of DS20006251A. It latches data on the rising edge of SCK and outputs on the falling edge - incompatible with Mode 1 (sample on rising, shift on falling) and Mode 2 (sample on falling, shift on rising). Attempting Mode 1/2 will result in corrupted reads/writes.

What happens to the STATUS register's BP1/BP0 bits after power cycling the AT25040B-XHL-T?

The BP1 and BP0 bits in the STATUS register of the AT25040B-XHL-T retain their last written values across power cycles because they are stored in nonvolatile EEPROM cells. As noted in Section 4.6.5 "Device Default State at Power-Up", these bits are "unchanged from their previous state" - unlike WEL or RDY/BSY, which reset to default logic states. This ensures persistent write protection configuration without host re-initialization.