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Microchip Technology 24LC21AT/SN
- Part No.:
- 24LC21AT/SN
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
24LC21AT/SN.pdf
- Description:
- IC EEPROM 1KBIT I2C 400KHZ 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,200
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Product details
Overview
24LC21AT/SN from Microchip Technology Inc. is a 128 × 8-bit dual-mode I²C-compatible serial EEPROM designed for display monitor identification (DDC1/DDC2) and configuration storage. It operates in Transmit-Only mode (VCLK-clocked, unidirectional EDID streaming) or Bidirectional mode (SCL-clocked, byte-addressable I²C read/write), supports 2.5–5.5V supply, delivers 1 mA active current, and retains data >200 years. Used in LCD/LED monitor EDID firmware storage.
For engineers reviewing the 24LC21AT/SN datasheet, 24LC21AT/SN pinout, 24LC21AT/SN application, or 24LC21AT/SN equivalent, key selection criteria include dual-mode DDC compliance, VCLK/SCL clock separation, write-protection via VCLK logic level, page-write buffer (8 bytes), and industrial-grade temperature operation (−40°C to +85°C).
Technical Context
The 24LC21AT/SN implements two independent 2-wire protocols sharing SDA: Transmit-Only mode uses VCLK for continuous EDID bitstream output (MSB-first, 9th null bit), while Bidirectional mode uses SCL for standard I²C communication with slave address 1010000X. Mode transition occurs only on valid high-to-low SCL edge; once in Bidirectional mode, power cycle is required to return to Transmit-Only mode.
Internal architecture includes EEPROM array with page latches, HV generator for write/erase, Schmitt-trigger inputs on SDA/SCL/VCLK (with 50 ns spike suppression), and VCC threshold detector disabling programming below 1.5V. Write protection is hardware-enforced: VCLK = low disables all writes, enabling ROM-like operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 128 × 8-bit (1 Kbit) EEPROM array with wraparound addressing in Transmit-Only mode. |
| Supply Voltage | 2.5V to 5.5V - enables direct interface with 3.3V and 5V display systems without level shifting. |
| Write Endurance | 1,000,000 erase/write cycles - ensures long-term reliability in field-updatable EDID applications. |
| Data Retention | >200 years at 25°C - guarantees persistent monitor identity and timing data across product lifetime. |
| I²C Speed | 100 kHz (2.5V) / 400 kHz (5V) - supports both legacy DDC1 and faster DDC2B communication. |
| Active Current | 1 mA typical at 5.5V - minimizes power draw during I²C read/write operations. |
| Standby Current | 10 μA typical at 5.5V - reduces quiescent power in always-on display subsystems. |
| ESD Protection | >4000V HBM - protects against electrostatic discharge during monitor assembly and handling. |
Pinout & Package
24LC21AT/SN is supplied in an 8-pin SOIC package (3.90 mm width), RoHS-compliant, with industrial temperature range (−40°C to +85°C). Pin 1 is marked with dot or bevel; pin numbering follows standard SOIC convention (counterclockwise from top-left corner).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VSS | Ground reference | Common return path for all internal circuits; must be connected to system ground plane. |
| SDA | Serial Data I/O | Open-drain bidirectional bus line shared by both modes; requires external pull-up resistor (2 kΩ for 400 kHz, 10 kΩ for 100 kHz). |
| SCL | Serial Clock (Bidirectional mode) | Input-only clock for I²C protocol; rising/falling edges synchronize data transfer; high-to-low transition triggers mode switch from Transmit-Only. |
| VCLK | Serial Clock (Transmit-Only mode) | Input-only clock for EDID streaming; rising edge clocks out MSB-first data bits; logic-high level required to enable writes in Bidirectional mode. |
| VCC | Power supply | 2.5–5.5V input powering EEPROM core, logic, and HV generator; includes internal VCC threshold detector. |
| NC | No connection | Unbonded die pad; must remain floating - no external connection permitted. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-mode DDC compliance | Fully implements DDC1™/DDC2™ standards for monitor identification - eliminates need for separate EDID PROM and I²C EEPROM. |
| Hardware write protection | VCLK pin doubles as write-enable control: logic low disables all memory writes, enabling secure ROM emulation. |
| Self-timed write cycle | Automated erase-before-write with internal timing (max 10 ms); no external delay required - simplifies firmware integration. |
| Page write buffer | 8-byte buffer allows burst programming of contiguous addresses - reduces I²C transaction overhead by 8× vs. byte writes. |
| Noise-immune interface | Schmitt-trigger inputs on SDA/SCL/VCLK plus 50 ns spike filtering - ensures robust operation on electrically noisy display PCBs. |
| Extended temperature range | Qualified for −40°C to +85°C operation - meets industrial and commercial display environmental requirements. |
Applications
| Monitor EDID Storage | Display Timing Configuration |
|---|---|
|
Use Scenario: Storing Extended Display Identification Data (EDID) in LCD/LED monitors for plug-and-play detection by host GPUs. IC Role / Device Role / Timing Role: Primary EDID PROM in DDC1/DDC2-compliant display subsystems; outputs fixed 128-byte EDID block continuously in Transmit-Only mode. Use Value: Enables automatic resolution/timing negotiation without host driver intervention; VCLK synchronization aligns EDID stream with VSYNC-derived clock. |
Use Scenario: Storing custom display timing parameters (e.g., CVT, GTF, or proprietary modes) accessible via I²C during dynamic resolution switching. IC Role / Device Role / Timing Role: Configurable timing parameter store accessed in Bidirectional mode; supports random reads and page writes for fast updates. Use Value: Allows field-upgradable timing tables without monitor firmware reflash; 1M endurance supports frequent calibration adjustments. |
| Embedded Display Interface | Industrial HMI Configuration |
|
Use Scenario: Providing plug-and-play display identity in embedded systems (e.g., medical displays, kiosks) where GPU-initiated DDC handshake is mandatory. IC Role / Device Role / Timing Role: Dual-role interface device: transmits static EDID on power-up, then accepts dynamic configuration writes via I²C after mode switch. Use Value: Eliminates need for separate EDID PROM and configuration EEPROM - reduces BOM count and PCB footprint. |
Use Scenario: Storing operator-configurable UI settings (language, brightness, contrast) in industrial human-machine interfaces with extended temperature requirements. IC Role / Device Role / Timing Role: Nonvolatile configuration store with hardware write protection (VCLK = low) preventing accidental overwrites during operation. Use Value: Ensures settings persistence across power cycles and thermal stress; >200-year data retention prevents field failures due to memory decay. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar serial EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 24LC21A-I/SN | Same die, identical electrical specs and pinout; differs only in temperature grade marking (I = industrial) and traceability code format. | No functional difference - both rated −40°C to +85°C; 24LC21A-I/SN is legacy marking variant of same production lot. | Select 24LC21AT/SN for new designs requiring latest Microchip date-code and Pb-free compliance documentation. |
| AT24C01C-SSHM-T | 1Kbit I²C EEPROM (128 × 8) with single-mode I²C interface only; no VCLK pin or Transmit-Only mode; supports 1 MHz Fast-mode Plus. | Lacks DDC1 compatibility - cannot replace 24LC21AT/SN in EDID streaming applications without redesigning clocking architecture. | Use only if Bidirectional mode suffices and VCLK-based EDID transmission is unnecessary; verify SDA/SCL timing margins at 1 MHz. |
Compared with 24LC21AT/SN, 24LC21A-I/SN offers identical functionality with minor packaging documentation differences, while AT24C01C-SSHM-T provides higher-speed I²C but sacrifices DDC1 compliance and dual-mode flexibility - making it unsuitable for monitor EDID replacement without system-level changes.
Availability
24LC21AT/SN is available at Aetrix Electronics and suitable for LCD monitor manufacturing, embedded display interface design, and industrial HMI configuration storage requiring stable component supply and long-term lifecycle support.
Supply support for 24LC21AT/SN 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 U.S.-based semiconductor company specializing in microcontrollers, analog devices, and memory products, with a focus on embedded control and connectivity solutions.
The 24LC21AT/SN belongs to Microchip's DDC-compliant serial EEPROM product line, engineered specifically for display industry EDID storage and timing configuration - balancing dual-mode flexibility, industrial reliability, and VESA standard adherence.
FAQ
What is the primary function of the VCLK pin on the 24LC21AT/SN?
The VCLK pin serves two distinct roles: in Transmit-Only mode, it acts as the clock input for continuous EDID bitstream output (rising-edge triggered); in Bidirectional mode, it functions as a hardware write-enable control - logic high permits writes, logic low disables all memory programming. This dual use enables seamless DDC1/DDC2 interoperability without external logic.
How does the 24LC21AT/SN switch between Transmit-Only and Bidirectional modes?
The 24LC21AT/SN powers up in Transmit-Only mode. A valid high-to-low transition on the SCL pin initiates transition to Bidirectional mode, where the device listens for its I²C slave address (1010000X). If detected, it remains in Bidirectional mode until power is cycled; if not received within 128 VCLK pulses, it reverts to Transmit-Only mode. No software command triggers this switch - it is purely hardware-synchronized.
Can the 24LC21AT/SN be used as a standard I²C EEPROM without DDC functionality?
Yes - the 24LC21AT/SN fully supports standard I²C byte and page writes/reads in Bidirectional mode using slave address 1010000X. Its DDC-specific features (VCLK, Transmit-Only mode) are inactive unless explicitly engaged; standard I²C transactions proceed identically to generic 1Kbit EEPROMs, with identical timing and acknowledgment behavior.
What is the maximum write speed and page size for the 24LC21AT/SN?
The 24LC21AT/SN supports page writes of up to 8 bytes per transaction, with a maximum I²C clock frequency of 400 kHz (at 4.5–5.5V). Each page write completes in ≤10 ms (self-timed), and the internal address pointer increments automatically across the 8-byte buffer - enabling efficient bulk configuration updates without host-side address management.
Is the 24LC21AT/SN pin-compatible with the original 24LC21?
Yes - the 24LC21AT/SN is explicitly documented as pin and function compatible with the 24LC21. Both share identical 8-pin SOIC/PDIP footprints, pin assignments (VSS, SDA, SCL, VCLK, VCC, NC), electrical characteristics, and dual-mode operation. The "T" suffix denotes tape-and-reel packaging, and "/SN" confirms SOIC package - no layout changes are needed for migration.
24LC21AT/SN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Programmable:
- Verified
- Memory Type:
- Non-Volatile
- Memory Format:
- EEPROM
- Technology:
- EEPROM
- Memory Size:
- 1Kbit
- Memory Organization:
- 128 x 8
- Memory Interface:
- I2C
- Clock Frequency:
- 400 kHz
- Write Cycle Time - Word, Page:
- 10ms
- Access Time:
- 900 ns
- Voltage - Supply:
- 2.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
24LC21AT/SN FAQ
1.How can I place an order for 24LC21AT/SN through Aetrix?
Please submit a Request for Quotation (RFQ) for 24LC21AT/SN 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 24LC21AT/SN reliable?
The price and inventory of 24LC21AT/SN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 24LC21AT/SN is usually 5 days.
3.What payment methods are accepted for 24LC21AT/SN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 24LC21AT/SN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 24LC21AT/SN?
24LC21AT/SN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 24LC21AT/SN 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 24LC21AT/SN?
For technical support, including 24LC21AT/SN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 24LC21AT/SN requirements.
6.How does Aetrix verify that 24LC21AT/SN is sourced from the original manufacturer or authorized distributors?
All 24LC21AT/SN 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 24LC21AT/SN meets industry standards.
7.What is the process for return or replacement of 24LC21AT/SN?
All 24LC21AT/SN units undergo pre-shipment inspection (PSI). If there is an issue with 24LC21AT/SN, 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 24LC21AT/SN part is unused and in its original packaging.
Return procedure for 24LC21AT/SN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
24LC21AT/SN Tags
-
M24C02-WMN6TP
STMicroelectronics
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AT24C02C-XHM-T
Microchip Technology
-
AT21CS01-STUM10-T
Microchip Technology
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AT24C02C-SSHM-T
Microchip Technology
-
24LC01BT-I/OT
Microchip Technology
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M24C02-FMC6TG
STMicroelectronics
-
AT24CS02-SSHM-T
Microchip Technology
-
93LC46BT-I/OT
Microchip Technology
-
AT24C04C-SSHM-T
Microchip Technology
-
24LC01BT-I/SN
Microchip Technology
-
24AA02UIDT-I/OT
Microchip Technology
-
AT24C08C-STUM-T
Microchip Technology
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