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Microchip Technology 25LC640AT-I/ST
- Part No.:
- 25LC640AT-I/ST
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 8-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
25LC640AT-I/ST.pdf
- Description:
- IC EEPROM 64KBIT SPI 8TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:17,654
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Product details
Overview
25LC640AT-I/ST from Microchip Technology Inc. is a 64-Kbit SPI Serial EEPROM with 8192 × 8-bit organization, 32-byte page size, and industrial temperature range (–40°C to +85°C). It operates at up to 10 MHz clock frequency with 5 mA read/write current at 5.5 V and supports hardware write protection via WP pin and STATUS register. It is used in microcontroller-based systems for nonvolatile parameter storage, calibration data retention, and firmware configuration.
For engineers reviewing the 25LC640AT-I/ST datasheet, 25LC640AT-I/ST pinout, 25LC640AT-I/ST application, or 25LC640AT-I/ST equivalent, key selection considerations include VCC range (2.5V–5.5V), SPI mode compatibility (Mode 0,0 and 1,1), HOLD functionality for interrupt-safe bus arbitration, and block-level write protection granularity (none/¼/½/all array).
Technical Context
The 25LC640AT-I/ST implements a standard SPI interface with separate SI (data in) and SO (data out) lines, CS-controlled device selection, and SCK-synchronized serial communication. It supports both byte and page write operations (up to 32 bytes per page), with self-timed internal write cycles completing in ≤5 ms.
Its architecture includes a write enable latch (WEL), status register with WIP/WEL/BP0/BP1 bits, and programmable hardware write protection enabled only when WPEN = 1 and WP = low. The HOLD pin suspends ongoing transfers without resetting the sequence, enabling deterministic host interrupt handling.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 64 Kbit (8192 × 8-bit), sufficient for storing boot parameters, sensor calibration tables, or device ID data in resource-constrained embedded systems. |
| Interface | SPI-compatible serial bus (Mode 0,0 and Mode 1,1), requiring only four signal lines (CS, SCK, SI, SO) for minimal PCB footprint and easy integration with PIC® and other MCU families. |
| Max Clock Frequency | 10 MHz at VCC ≥ 4.5 V - enables fast read/write throughput (e.g., ~3.2 µs per byte read); drops to 5 MHz at 2.5–4.5 V for robust operation across wide supply ranges. |
| Write Cycle Time | ≤5 ms internal write cycle - eliminates need for external polling delay; WIP bit allows software-driven status checking during writes. |
| Endurance & Retention | 1,000,000 erase/write cycles and >200 years data retention - suitable for field-updatable systems requiring long-term reliability without wear leveling. |
| Supply Voltage | 2.5 V to 5.5 V - compatible with 3.3 V and 5 V logic domains, eliminating level-shifting in mixed-voltage designs. |
| Temperature Range | Industrial grade (–40°C to +85°C) - validated for use in automotive control modules, industrial HMIs, and outdoor IoT edge nodes. |
Pinout & Package
25LC640AT-I/ST is packaged in an 8-lead SOIC (SN) with 150-mil body width and standard JEDEC MS-012AC outline. Pin 1 is marked with a beveled corner or dot; package meets RoHS requirements and is rated for industrial temperature operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| CS (Pin 1) | Chip Select Input | Active-low enable: pulls device into active state; rising edge initiates internal write cycle; high-Z SO when deasserted enables multi-device SPI bus sharing. |
| SO (Pin 2) | Serial Output | Data output line: shifts out memory contents on falling edge of SCK; tri-states when CS high or HOLD low. |
| WP (Pin 3) | Write-Protect Input | Hardware lock: disables STATUS register writes when WPEN = 1 and WP = low; no effect on memory reads or if WPEN = 0. |
| VSS (Pin 4) | Ground | Reference return path for all digital and analog circuitry; must be low-impedance connection to minimize noise coupling. |
| SI (Pin 5) | Serial Input | Data/command input: latches instructions, addresses, and write data on rising edge of SCK; requires clean setup/hold timing per AC specs. |
| SCK (Pin 6) | Serial Clock | Master-generated clock: synchronizes all SI sampling and SO updates; max 10 MHz rate defines maximum sustained data transfer bandwidth. |
| HOLD (Pin 7) | Hold Input | Bus pause control: suspends ongoing SPI transfer when pulled low while SCK is low; resumes on rising HOLD edge with SCK low - critical for real-time interrupt servicing. |
| VCC (Pin 8) | Supply Voltage | Power input: accepts 2.5–5.5 V; internal regulation ensures stable core voltage; decoupling capacitor (0.1 µF) required near pin. |
Key Features
| Feature | Design Value |
|---|---|
| 32-byte page write | Enables efficient bulk programming within single physical page boundaries (0x0000–0x001F, etc.), reducing command overhead vs. byte writes - but requires firmware to avoid crossing page boundaries. |
| Block write protection | Configurable via BP0/BP1 bits to protect none, upper 1/4 (0x1800–0x1FFF), upper 1/2 (0x1000–0x1FFF), or entire array - prevents accidental overwrites of critical firmware or calibration sectors. |
| HOLD pin functionality | Allows deterministic suspension/resumption of SPI transfers without losing byte alignment or address pointer state - essential for time-critical host interrupt response in real-time systems. |
| Power-on write disable | Write enable latch resets at power-up, preventing spurious writes during supply ramp; explicit WREN instruction required before any write - enhances system robustness during brown-out conditions. |
| ESD tolerance | ≥4 kV HBM rating on all pins - reduces need for external ESD protection in board-level designs targeting IEC 61000-4-2 Level 2 compliance. |
Applications
| Industrial Sensor Node | Automotive Body Control Module |
|---|---|
Use Scenario: Storing calibrated offset/gain values for temperature, pressure, and humidity sensors deployed in factory-floor monitoring systems. IC Role / Device Role / Timing Role: Nonvolatile configuration storage accessed during MCU boot and runtime recalibration; SPI interface synchronized to MCU's peripheral clock. Use Value: Enables field-replaceable sensor units with unique calibration profiles retained across power cycles and firmware updates - no re-calibration needed after replacement. | Use Scenario: Holding seat position memory, mirror angle presets, and lighting configuration in 12 V automotive cabin electronics. IC Role / Device Role / Timing Role: SPI-connected EEPROM storing user preferences; accessed during ignition-on initialization and updated on change events. Use Value: Survives battery disconnects and meets AEC-Q100 Grade 2 requirements; hardware WP pin prevents corruption during load dump transients. |
| Medical Infusion Pump | Smart Energy Meter |
Use Scenario: Recording dose history, alarm logs, and maintenance counters in Class II medical devices requiring traceable event storage. IC Role / Device Role / Timing Role: Fault-tolerant data logger interfaced via isolated SPI; write operations guarded by WREN/WRSR sequences and BP bits. Use Value: 1M endurance and >200-year retention satisfy FDA 21 CFR Part 11 electronic record longevity requirements without external backup power. | Use Scenario: Storing tariff schedules, metering constants, and tamper-event timestamps in ANSI C12.20-compliant electricity meters. IC Role / Device Role / Timing Role: Secure configuration store with hardware write protection activated during normal operation to prevent unauthorized parameter changes. Use Value: Block protection (BP1/BP0) isolates utility-programmable fields from customer-accessible registers - simplifies certification and field update workflows. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar serial EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 25AA640AT-I/ST | VCC range 1.8–5.5 V; supports lower-voltage operation down to 1.8 V; otherwise identical pinout, timing, and feature set. | Suitable for battery-powered or ultra-low-power systems where supply may dip below 2.5 V during brown-out. | Select when operating voltage may fall below 2.5 V; verify hold time and clock timing margins at 1.8 V per DS20001830G Table 1-2. |
| AT25DF641A-SH-B | 64 Mbit density, quad SPI interface, 8-pin SOIC package; not pin-compatible; requires different command set and driver stack. | Targeted at high-speed firmware storage (e.g., code shadowing), not parameter/configuration storage. | Only consider for capacity- or speed-driven upgrades; requires full firmware redesign and layout change - not a drop-in replacement. |
Compared with 25AA640AT-I/ST, the 25LC640AT-I/ST offers tighter VCC lower limit exclusion (2.5 V min), simplifying power domain design in 3.3 V-only systems; versus AT25DF641A-SH-B, it provides proven reliability for small-data, high-endurance use cases without SPI protocol complexity or layout rework.
Availability
25LC640AT-I/ST is available at Aetrix Electronics and suitable for industrial automation controllers, automotive body electronics, medical instrumentation, and smart metering applications requiring stable component supply, long-term lifecycle support, and AEC-Q100-qualified nonvolatile memory.
Supply support for 25LC640AT-I/ST 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 25LC640A family was designed specifically for reliable, low-power, SPI-based configuration and calibration data storage in industrial, automotive, and medical systems - emphasizing endurance, data retention, and hardware-assisted write protection.
FAQ
What is the minimum VCC required for reliable operation of the 25LC640AT-I/ST?
The 25LC640AT-I/ST requires a minimum VCC of 2.5 V for guaranteed operation across its full industrial temperature range (–40°C to +85°C). Below 2.5 V, timing parameters degrade and write functionality is not assured. This distinguishes it from the 25AA640AT-I/ST, which supports down to 1.8 V. Always reference DS20001830G Table 1-1 and Table 1-2 for voltage-dependent AC/DC specs when designing with the 25LC640AT-I/ST.
Does the 25LC640AT-I/ST support SPI Mode 0,0 and Mode 1,1 simultaneously?
Yes, the 25LC640AT-I/ST supports both SPI Mode 0,0 (CPOL = 0, CPHA = 0) and Mode 1,1 (CPOL = 1, CPHA = 1) as defined by its SCK idle state and sampling edge behavior. The device does not auto-detect mode; the host MCU must configure its SPI peripheral accordingly. Both modes are fully characterized in the datasheet (DS20001830G Figure 1-2 and Figure 1-3), and timing margins are specified for each. No configuration register or external setting is needed to switch between them - it is purely a host-side interface choice.
How does the HOLD pin function during an active write cycle in the 25LC640AT-I/ST?
The HOLD pin has no effect on an ongoing internal write cycle in the 25LC640AT-I/ST. Once CS rises after a valid WRITE or WRSR command, the device initiates its self-timed 5 ms write cycle, during which HOLD is ignored. HOLD only affects serial communication (read/write instructions, address/data transfer) - not the internal EEPROM programming phase. During that phase, the WIP bit remains set and SO is high-impedance regardless of HOLD state. This behavior is explicitly documented in Section 2.6 and Figure 3-2 of DS20001830G.
Can the 25LC640AT-I/ST be used in automotive applications requiring AEC-Q100 qualification?
Yes, the 25LC640AT-I/ST is AEC-Q100 qualified for automotive applications. The "I" suffix denotes Industrial temperature grade (–40°C to +85°C), and the device is explicitly listed in the datasheet as "Automotive AEC-Q100 Qualified". It meets stress test requirements for temperature cycling, HTOL, and ESD per AEC-Q100 Rev G. However, note that this qualification applies to the 25LC640A part number family - always verify the specific date code and packaging (e.g., T/ST suffix) against Microchip's latest AEC-Q100 certificate for 25LC640AT-I/ST before automotive production release.
What happens to the write enable latch after a successful write operation in the 25LC640AT-I/ST?
After a successful WRITE, WRSR, or WRDI instruction, the write enable latch (WEL bit in STATUS register) is automatically reset to '0' in the 25LC640AT-I/ST. This means the device immediately reverts to write-disabled state, requiring a new WREN instruction before any subsequent write attempt. This behavior is enforced by hardware and occurs regardless of WP pin state or BP bits. It is a fundamental safety feature to prevent unintended writes - confirmed in Section 3.4 and Table 5-1 of DS20001830G, and applies identically to all 25XX640A variants including the 25LC640AT-I/ST.
25LC640AT-I/ST Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 8-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Programmable:
- Not Verified
- Memory Type:
- Non-Volatile
- Memory Format:
- EEPROM
- Technology:
- EEPROM
- Memory Size:
- 64Kbit
- Memory Organization:
- 8K x 8
- Memory Interface:
- SPI
- Clock Frequency:
- 10 MHz
- Write Cycle Time - Word, Page:
- 5ms
- Access Time:
- -
- Voltage - Supply:
- 2.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-TSSOP
25LC640AT-I/ST FAQ
1.How can I place an order for 25LC640AT-I/ST through Aetrix?
Please submit a Request for Quotation (RFQ) for 25LC640AT-I/ST on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for 25LC640AT-I/ST reliable?
The price and inventory of 25LC640AT-I/ST are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 25LC640AT-I/ST is usually 5 days.
3.What payment methods are accepted for 25LC640AT-I/ST?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 25LC640AT-I/ST transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 25LC640AT-I/ST?
25LC640AT-I/ST orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 25LC640AT-I/ST order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for 25LC640AT-I/ST?
For technical support, including 25LC640AT-I/ST datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 25LC640AT-I/ST requirements.
6.How does Aetrix verify that 25LC640AT-I/ST is sourced from the original manufacturer or authorized distributors?
All 25LC640AT-I/ST products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that 25LC640AT-I/ST meets industry standards.
7.What is the process for return or replacement of 25LC640AT-I/ST?
All 25LC640AT-I/ST units undergo pre-shipment inspection (PSI). If there is an issue with 25LC640AT-I/ST, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The 25LC640AT-I/ST part is unused and in its original packaging.
Return procedure for 25LC640AT-I/ST:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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