Microchip Technology AT25040B-SSHL-T

Overview

AT25040B-SSHL-T from Microchip Technology is a 4-Kbit SPI Serial EEPROM organized as 512 × 8 bits, operating from 1.8V to 5.5V with industrial temperature range (−40°C to +85°C), 20 MHz max clock rate at 5V, and hardware/software write protection via WP pin and STATUS register. It serves as nonvolatile configuration storage in microcontroller-based embedded systems requiring reliable, low-power data retention.

For engineers reviewing the AT25040B-SSHL-T datasheet, AT25040B-SSHL-T pinout, AT25040B-SSHL-T application, or AT25040B-SSHL-T equivalent, key selection considerations include SPI Mode 0/3 compatibility, 8-byte page write capability, block-level write protection (1/4, 1/2, or full array), 5 ms max self-timed write cycle, and SOIC-8 packaging with RoHS-compliant lead-free finish.

Technical Context

The AT25040B-SSHL-T implements a synchronous SPI slave interface with fixed MSB-first data framing, rising-edge input sampling (SI), and falling-edge output timing (SO). Its internal architecture includes a high-voltage generation circuit for EEPROM programming, a STATUS register with BP1/BP0 bits for nonvolatile block protection, and dedicated HOLD and WP pins for real-time serial suspension and hardware write inhibition.

It supports dual SPI modes (0 and 3) with identical data timing but differing SCK idle polarity; mode selection is determined by host controller configuration-not device setting. The device enters standby mode on CS deassertion, resets WEL on CS toggle, and maintains nonvolatile BP bits across power cycles-enabling persistent memory protection without firmware reinitialization.

Key Specifications

Pinout & Package

AT25040B-SSHL-T is supplied in an 8-lead SOIC package (3.9 mm × 4.9 mm, 1.27 mm pitch) with standard JEDEC MS-012AC footprint and RoHS-compliant matte tin plating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with M95040-DRMN6TP/K and CAT25040VI-GT3, the AT25040B-SSHL-T uniquely combines HOLD functionality, dual SPI mode support, and consistent 20 MHz operation across its full voltage range-making it optimal for real-time embedded systems requiring deterministic serial bus arbitration and flexible host compatibility.

Availability

AT25040B-SSHL-T is available at Aetrix Electronics and suitable for industrial sensor nodes, medical diagnostic devices, automotive body control modules, smart energy meters, and IoT edge gateways requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant manufacturing.

Supply support for AT25040B-SSHL-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 microcontrollers, analog components, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.

The AT25040B-SSHL-T belongs to Microchip's AT25xxx-B series of SPI Serial EEPROMs, engineered for robust nonvolatile data storage in resource-constrained embedded systems where reliability, low-voltage operation, and industrial temperature tolerance are mandatory.

FAQ

What is the memory organization of the AT25040B-SSHL-T?

The AT25040B-SSHL-T contains 4,096 bits of EEPROM memory organized as 512 words × 8 bits. This structure supports byte-addressable random access and 8-byte page write operations. The memory map is linear with no internal bank switching, and all addresses are accessed using a 9-bit address field in the WRITE and READ opcodes-ensuring straightforward integration with 8-bit and 32-bit microcontrollers alike. The AT25040B-SSHL-T shares this organization with the AT25010B and AT25020B variants but scales capacity to meet mid-range configuration storage needs.

Does the AT25040B-SSHL-T support SPI Mode 3, and how is it configured?

Yes, the AT25040B-SSHL-T supports both SPI Mode 0 (CPOL = 0, CPHA = 0) and SPI Mode 3 (CPOL = 1, CPHA = 0). Configuration is handled entirely by the host controller-the device has no internal mode register. In Mode 3, the SCK line idles high when CS is deasserted, and data is still sampled on the rising edge and output on the falling edge. The AT25040B-SSHL-T automatically adapts to the host's SCK idle state; no device-side setup is required. This dual-mode capability ensures interoperability with legacy and modern SPI peripherals without firmware modification.

How does the Write-Protect (WP) pin interact with the STATUS register protection bits in the AT25040B-SSHL-T?

In the AT25040B-SSHL-T, the WP pin and STATUS register BP1/BP0 bits provide independent, hierarchical protection. When WP is low, all write operations-including WRSR-are blocked regardless of BP bit values. When WP is high, BP1/BP0 determine which memory segments (none, 1/4, 1/2, or full array) are software-protected. The AT25040B-SSHL-T allows simultaneous use: e.g., WP can be used for field-service lockout while BP bits preserve factory calibration data. Critically, WP assertion during an active write cycle halts instruction acceptance but does not abort an already-initiated internal write-ensuring data integrity.

What is the purpose of the HOLD pin in the AT25040B-SSHL-T, and does it affect ongoing write cycles?

The HOLD pin in the AT25040B-SSHL-T suspends serial communication without resetting the instruction state-allowing the host to pause data transfers during higher-priority interrupts. When asserted (low) with CS active and SCK low, SO immediately enters high-impedance and SI/SCK inputs are ignored. However, HOLD has no effect on internal operations: if a write cycle is already executing, it completes uninterrupted. Once HOLD is deasserted, the transaction resumes from the exact bit position. This behavior makes the AT25040B-SSHL-T suitable for deterministic real-time systems where bus arbitration must not corrupt EEPROM state.

Is the AT25040B-SSHL-T compatible with 1.8V-only systems, and what performance trade-offs apply?

Yes, the AT25040B-SSHL-T is fully specified for 1.8V operation across its industrial temperature range. At 1.8V, maximum SCK frequency is 5 MHz (vs. 20 MHz at 5V), and standby current rises to 0.5 µA (ISB1). DC parameters including VOL2 (≤0.2V) and VOH2 (≥VCC − 0.2V) ensure clean logic levels into 1.8V CMOS inputs. The 5 ms write cycle time remains unchanged. These characteristics make the AT25040B-SSHL-T viable for ultra-low-power wearables and battery-powered sensors-provided host firmware adjusts SPI clock dividers and validates timing margins per Table 4-3 in the datasheet.