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Microchip Technology 24LC21A-I/P
- Part No.:
- 24LC21A-I/P
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
24LC21A-I/P.pdf
- Description:
- IC EEPROM 1KBIT I2C 400KHZ 8DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,035
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Product details
Overview
24LC21A-I/P 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 from 2.5V to 5.5V, supports both Transmit-Only (VCLK-clocked) and Bidirectional (SCL-clocked) modes, delivers 1 mA active current, and features 1,000,000 erase/write cycles with >200-year data retention.
For engineers reviewing the 24LC21A-I/P datasheet, 24LC21A-I/P pinout, 24LC21A-I/P application, or 24LC21A-I/P equivalent, this device serves as a DDC-compliant memory solution requiring dual-clock interface handling, write-protection via VCLK logic level, and seamless integration into EDID transmission paths in display subsystems.
Technical Context
The 24LC21A-I/P implements two distinct operational modes: Transmit-Only mode (VCLK-driven, unidirectional EDID streaming at address 00h–7Fh) and Bidirectional mode (I²C-compliant slave with 7-bit address 1010000X). Mode transition occurs only on a valid high-to-low SCL edge, after which the device remains in Bidirectional mode until power cycle.
Its internal architecture includes a page write buffer (8 bytes), HV generator for EEPROM programming, Schmitt-trigger inputs on SDA/SCL/VCLK for noise immunity, and VCC threshold detection disabling writes below 1.5V. Write enable requires VCLK = high during command/data transfer; VCLK is ignored during self-timed write cycles.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory size | 128 × 8-bit (1 Kbit) EEPROM array, organized as 128 sequential addresses (00h–7Fh) |
| Supply voltage | 2.5V to 5.5V - enables direct interface with 3.3V and 5V display systems without level shifting |
| I²C speed | 100 kHz (at 2.5V) / 400 kHz (at 4.5–5.5V) - supports standard and fast-mode timing compliance |
| 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 storage over product lifetime |
| Active current | 1 mA typical at 5.5V - minimizes power impact in always-on display interface circuits |
| Standby current | 10 μA typical at 5.5V - reduces quiescent draw when idle in DDC bus |
Pinout & Package
24LC21A-I/P is housed in an 8-pin PDIP (Plastic Dual In-line Package) with 300-mil body width, rated for industrial temperature range (−40°C to +85°C) and RoHS-compliant matte tin plating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VSS | Ground reference | System common return path; must be low-impedance connection to minimize noise coupling into sensitive DDC signaling |
| SDA | Serial data I/O | Open-drain bidirectional bus line shared between both modes; requires external pull-up (2–10 kΩ) per I²C specification |
| SCL | Bidirectional mode clock input | Master-generated clock for I²C transactions; also triggers mode transition from Transmit-Only to Bidirectional on high-to-low edge |
| VCLK | Transmit-Only mode clock input | Drives EDID bitstream output in DDC1 mode; must be held high to enable writes in Bidirectional mode |
| VCC | Power supply | 2.5–5.5V supply with internal VCC threshold detector - disables writes if voltage drops below ~1.5V |
| NC | No connection | Pins 1, 2, 3 are unconnected; must remain floating or tied to ground per layout best practice (not driven) |
Key Features
| Feature | Design Value |
|---|---|
| Dual-mode operation | Supports both continuous EDID broadcast (VCLK-clocked) and random-access I²C reads/writes - eliminates need for separate ROM + EEPROM in DDC designs |
| VCLK-based write protection | Setting VCLK = low disables all writes in Bidirectional mode - provides hardware-level memory lock without external logic |
| Page write buffer | Accepts up to eight bytes before initiating internal write cycle - reduces bus occupancy and improves firmware efficiency during multi-byte updates |
| DDC1/DDC2 compliance | Fully implements VESA DDC Standard (excluding Access.bus) - ensures plug-and-play interoperability with graphics controllers and monitors |
| ESD robustness | >4000V HBM on all pins - withstands electrostatic discharge events common in display assembly and field service environments |
Applications
| Monitor EDID Storage | Display Configuration Memory |
|---|---|
Use Scenario: Storing Extended Display Identification Data (EDID) in LCD/LED monitors for automatic resolution and timing negotiation with host GPUs. IC Role / Device Role / Timing Role: Primary nonvolatile memory source for DDC1 (VCLK-clocked) and DDC2 (I²C-clocked) protocols; outputs fixed 128-byte EDID block on power-up. Use Value: Enables zero-configuration plug-and-play operation; eliminates manual display setup and ensures accurate color/timing metadata delivery to host system. | Use Scenario: Retaining user-adjusted display settings (brightness, contrast, color balance) across power cycles in commercial signage and medical displays. IC Role / Device Role / Timing Role: Configurable slave EEPROM accessed via I²C during boot or runtime; supports byte/page writes and sequential reads for efficient parameter management. Use Value: Preserves calibrated settings without battery backup; leverages 1M endurance to support frequent UI adjustments in field-deployed equipment. |
| Graphics Adapter Identity | Embedded System Boot Configuration |
Use Scenario: Providing vendor-specific capability descriptors and timing limits to GPU drivers in docking stations and external graphics adapters. IC Role / Device Role / Timing Role: I²C slave responding to address 1010000X; stores custom extension blocks beyond standard EDID, readable during driver enumeration. Use Value: Enables proprietary feature enablement (e.g., HDR metadata, adaptive sync) without modifying core GPU firmware - accelerates OEM differentiation. | Use Scenario: Holding board-specific calibration coefficients and hardware revision flags in industrial HMIs and test equipment with display interfaces. IC Role / Device Role / Timing Role: Dual-mode memory used for factory-programmed identifiers (Transmit-Only) and field-updatable parameters (Bidirectional); accessed early in boot sequence. Use Value: Separates immutable identity (VCLK stream) from mutable configuration (I²C), simplifying secure firmware update and traceability workflows. |
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 | Identical electrical and functional specifications; differs only in SOIC-8 package (3.9 mm width) instead of PDIP | Used where PCB space constraints or automated assembly favor surface-mount packaging | Select 24LC21A-I/SN for SMT production; pinout and timing match 24LC21A-I/P exactly |
| AT24C01C-PU | 1K-bit I²C EEPROM with single-mode (I²C-only) operation; no VCLK pin or Transmit-Only mode; max 1 MHz clock (5V) | Lacks DDC1 compatibility and automatic EDID streaming - requires host-controlled read initiation | Choose AT24C01C-PU only if DDC1 functionality is unnecessary and board already uses standard I²C EEPROM footprint |
Compared with 24LC21A-I/P, the 24LC21A-I/SN offers identical dual-mode functionality in a space-saving SOIC package, while the AT24C01C-PU sacrifices DDC1 compliance for higher I²C speed and simplified interface - making it unsuitable for monitor EDID but viable for general-purpose configuration storage.
Availability
24LC21A-I/P is available at Aetrix Electronics and suitable for display monitor manufacturing, graphics adapter design, and embedded HMI development requiring stable component supply, long-lifecycle support, and DDC protocol compliance.
Supply support for 24LC21A-I/P 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 manufacturer specializing in microcontrollers, analog devices, and memory products for industrial, automotive, and consumer applications.
The 24LC21A belongs to Microchip's legacy serial EEPROM family engineered specifically for Video Electronics Standards Association (VESA) DDC compliance - prioritizing dual-clock interface flexibility, EDID streaming reliability, and robustness in display interface environments.
FAQ
What is the primary function of the VCLK pin on the 24LC21A-I/P?
The VCLK pin on the 24LC21A-I/P serves two critical roles: in Transmit-Only mode, it clocks out EDID data bits on the rising edge for DDC1 compliance; in Bidirectional mode, it acts as a hardware write-enable signal - writes are only permitted when VCLK is held high. This dual function eliminates external logic for mode selection and memory protection in display systems.
How does the 24LC21A-I/P switch between Transmit-Only and Bidirectional modes?
The 24LC21A-I/P powers up in Transmit-Only mode and remains there as long as SCL is held high. A valid high-to-low transition on SCL initiates transition to Bidirectional mode, where the device listens for its I²C slave address (1010000X). If detected, it enters Bidirectional mode permanently until power is cycled - no software command or VCLK manipulation can revert it without power loss.
Can the 24LC21A-I/P be used as a standard I²C EEPROM without DDC functionality?
Yes, the 24LC21A-I/P functions fully as a standard I²C EEPROM in Bidirectional mode: it supports byte and page writes, current/random/sequential reads, and ACK polling. Its DDC1 Transmit-Only mode is optional and inactive unless VCLK is driven - so standard I²C systems can ignore VCLK (tie high) and use only SDA/SCL, retaining full compatibility with existing EEPROM drivers.
What is the maximum clock frequency supported by the 24LC21A-I/P in Bidirectional mode?
The 24LC21A-I/P supports 100 kHz operation across its full 2.5–5.5V supply range, and 400 kHz operation when VCC is 4.5–5.5V. These values are specified in the AC Characteristics table (DS21160G, page 3) and reflect guaranteed timing margins - not theoretical limits - ensuring reliable communication in electrically noisy display interface environments.
Does the 24LC21A-I/P require external pull-up resistors on SDA and SCL lines?
Yes, the 24LC21A-I/P has open-drain SDA and SCL outputs (SCL only in Bidirectional mode; SDA in both modes), requiring external pull-up resistors to VCC. Recommended values are 10 kΩ for 100 kHz operation and 2 kΩ for 400 kHz, as stated in Section 8.1 of the datasheet - insufficient pull-up strength causes timing violations and bus lockup during ACK/NACK phases.
24LC21A-I/P Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- 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:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-PDIP
24LC21A-I/P FAQ
1.How can I place an order for 24LC21A-I/P through Aetrix?
Please submit a Request for Quotation (RFQ) for 24LC21A-I/P 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 24LC21A-I/P reliable?
The price and inventory of 24LC21A-I/P are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 24LC21A-I/P is usually 5 days.
3.What payment methods are accepted for 24LC21A-I/P?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 24LC21A-I/P transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 24LC21A-I/P?
24LC21A-I/P orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 24LC21A-I/P 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 24LC21A-I/P?
For technical support, including 24LC21A-I/P datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 24LC21A-I/P requirements.
6.How does Aetrix verify that 24LC21A-I/P is sourced from the original manufacturer or authorized distributors?
All 24LC21A-I/P 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 24LC21A-I/P meets industry standards.
7.What is the process for return or replacement of 24LC21A-I/P?
All 24LC21A-I/P units undergo pre-shipment inspection (PSI). If there is an issue with 24LC21A-I/P, 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 24LC21A-I/P part is unused and in its original packaging.
Return procedure for 24LC21A-I/P:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
24LC21A-I/P Tags
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