Microchip Technology AT25640B-SSHL-T

Overview

AT25640B-SSHL-T from Microchip Technology (formerly Atmel) is a 64Kb SPI Serial EEPROM organized as 8,192 words × 8 bits, operating from 1.8V to 5.5V with 20MHz max clock rate at 5V, 32-byte page write capability, and hardware/software write protection via WP pin and status register. It serves as nonvolatile configuration storage in industrial controllers, power supply monitors, and embedded sensor nodes requiring long-term data retention.

For engineers reviewing the AT25640B-SSHL-T datasheet, AT25640B-SSHL-T pinout, AT25640B-SSHL-T application, or AT25640B-SSHL-T equivalent, key selection criteria include its JEDEC SOIC-8 package, -40°C to +85°C industrial temperature range, 1,000,000 write endurance, 100-year data retention, and support for SPI Modes 0 and 3 with HOLD/CS suspension logic.

Technical Context

The AT25640B-SSHL-T implements a synchronous SPI slave interface with separate SI (input) and SO (output) pins, MSB-first data framing, and opcode-driven command execution (e.g., WREN, WRITE, RDSR). Its internal architecture includes an 8-bit instruction register, address decoder, and status register with nonvolatile BP0/BP1 block protection bits and WPEN control.

Write operations require explicit Write Enable (WREN) before WRITE or WRSR commands; self-timed internal write cycles complete in ≤5ms with automatic return to write-disable state. The HOLD pin suspends serial communication without resetting the sequence when asserted low during SCK low time, enabling multi-device arbitration in shared bus systems.

Key Specifications

Pinout & Package

AT25640B-SSHL-T uses an 8-lead JEDEC SOIC package (8S1), 0.15" wide, with gull-wing leads and NiPdAu lead finish. Pin 1 is marked by a notch or dot; body dimensions are 4.80–5.05mm × 3.81–3.99mm × 1.35–1.75mm height.

Key Features

Applications

Equivalent & Alternatives

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

Compared with M95640-DRMN6TP/K and 25AA640A-I/SN, AT25640B-SSHL-T provides optimal balance of industrial temperature rating, HOLD-enabled bus flexibility, and JEDEC SOIC-8 drop-in compatibility-making it ideal for cost-sensitive, space-constrained industrial controllers.

Availability

AT25640B-SSHL-T is available at Aetrix Electronics and suitable for industrial PLCs, smart energy meters, medical infusion pumps, and automotive body control modules requiring stable component supply across long production lifecycles.

Supply support for AT25640B-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 acquired Atmel in 2016 and maintains full product support, documentation, and manufacturing continuity for legacy Atmel serial EEPROMs.

The AT25640B belongs to Atmel's SPI Serial EEPROM family, designed specifically for robust, low-power nonvolatile storage in resource-constrained embedded systems where reliability and long-term data integrity are critical.

FAQ

What is the maximum SPI clock frequency supported by the AT25640B-SSHL-T?

The AT25640B-SSHL-T supports up to 20MHz SCK frequency when VCC = 5.0V. At lower voltages (e.g., 1.8V–3.6V), the maximum clock rate reduces to 5MHz. These limits are defined in Table 4-3 of the datasheet and must be observed to ensure reliable read/write timing margins.

Does the AT25640B-SSHL-T support both SPI Mode 0 and Mode 3?

Yes, the AT25640B-SSHL-T supports SPI Modes 0 (CPOL = 0, CPHA = 0) and 3 (CPOL = 1, CPHA = 1), as explicitly stated in the Features section. The datasheet describes Mode 0 operation in detail, but Mode 3 is fully functional and verified in characterization testing.

How does the HOLD pin function during an active SPI transaction?

When the HOLD pin is driven low while SCK is low, the AT25640B-SSHL-T immediately suspends serial communication without resetting the internal address counter or command state. Communication resumes on the next rising edge of HOLD while SCK remains low, preserving full transaction context.

Can the AT25640B-SSHL-T be used in a 1.8V-only system?

Yes, the AT25640B-SSHL-T is fully specified for 1.8V operation (VCC = 1.8V to 5.5V), including AC timing, DC characteristics, and write endurance. Its L-suffix denotes wide-voltage capability, and all parameters in Tables 4-2 and 4-3 apply down to 1.8V.

What is the purpose of the WPEN bit in the status register of the AT25640B-SSHL-T?

The WPEN bit (bit 7) enables or disables hardware write protection via the WP pin. When WPEN = 1 and WP = low, writes to the status register-including BP0/BP1 and WPEN itself-are blocked. When WPEN = 0, the WP pin has no effect, allowing status register updates even with WP tied to ground.