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Microchip Technology 24LCS21AT-I/SN
- Part No.:
- 24LCS21AT-I/SN
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
24LCS21AT-I/SN.pdf
- Description:
- IC EEPROM 1KBIT I2C 400KHZ 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,082
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Product details
Overview
24LCS21AT-I/SN from Microchip Technology Inc. is a 128 × 8-bit dual-mode I²C™-compatible serial EEPROM designed for display configuration storage and DDC1/DDC2™ monitor identification. It operates from 2.5V to 5.5V, supports Transmit-Only (DDC1) and Bidirectional (I²C) modes, features hardware write-protection via WP pin, and delivers 1 mA active current and 10 μA standby current at 5.5V. It is used in LCD/LED monitor EDID storage circuits where reliable, low-power, mode-switchable memory is required.
For engineers reviewing the 24LCS21AT-I/SN datasheet, 24LCS21AT-I/SN pinout, 24LCS21AT-I/SN application, or 24LCS21AT-I/SN equivalent, key selection considerations include dual-mode clock handling (VCLK vs. SCL), flexible write-protection logic (WP + VCLK interaction), guaranteed 1 million erase/write cycles, 200-year data retention, and industrial temperature support (–40°C to +85°C).
Technical Context
The 24LCS21AT-I/SN implements two independent communication protocols on shared SDA: Transmit-Only mode uses VCLK as clock input and outputs sequential memory contents (00h–7Fh) MSB-first with null-bit framing; Bidirectional mode uses SCL for I²C timing and responds only to slave address 1010000X. Mode transition occurs on valid high-to-low SCL edge, followed by control byte detection - failure triggers automatic reversion to Transmit-Only after 128 VCLK pulses.
Write protection is implemented via dual-layer control: factory-default fuse unprogrammed enables write when VCLK = high; writing any value to address 7Fh programs the fuse, thereafter requiring both VCLK = high AND WP = high for writes. The device includes Schmitt-trigger inputs on SDA, SCL, and VCLK with 50 ns spike suppression and hysteresis, plus VCC threshold detection disabling programming below 1.5V.
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 subsystems without level shifting |
| I²C speed | 100 kHz at 2.5V / 400 kHz at 5V - supports standard and fast-mode timing for host controller compatibility |
| Write endurance | 1,000,000 erase/write cycles - ensures long-term reliability in dynamic EDID update scenarios |
| Data retention | >200 years at 25°C - guarantees persistent monitor identity and capability data across product lifetime |
| Operating temp | –40°C to +85°C (Industrial grade) - qualified for use inside enclosed display enclosures with thermal cycling |
| ESD rating | >4000V HBM - protects against electrostatic discharge during panel assembly and field service |
Pinout & Package
24LCS21AT-I/SN is housed in an 8-pin plastic SOIC package (150 mil body width), pin-compatible with industry-standard 8-lead SOIC footprints and suitable for automated surface-mount assembly.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (NC) | No Connection | Unbonded die pad - must remain floating; no external connection permitted |
| 2 (NC) | No Connection | Unbonded die pad - must remain floating; no external connection permitted |
| 3 (WP) | Write-Protect Input | Active-low enable: controls write access only after fuse programming at address 7Fh; requires pull-up for normal operation |
| 4 (VSS) | Ground Reference | Primary return path for all internal circuitry and I/O drivers; must be low-impedance connection to system ground plane |
| 5 (SDA) | Serial Data I/O | Open-drain bidirectional bus line - requires external pull-up (1 kΩ @ 400 kHz, 10 kΩ @ 100 kHz); shared between both operating modes |
| 6 (SCL) | I²C Clock Input | Master-generated clock for Bidirectional mode; also serves as mode-transition trigger (high-to-low edge) from Transmit-Only mode |
| 7 (VCLK) | Transmit-Only Clock | Input for DDC1 mode clocking; must be held high to enable writes in Bidirectional mode; ignored during self-timed write cycle |
| 8 (VCC) | Power Supply | 2.5V–5.5V supply input - includes internal VCC threshold detector that disables programming if voltage drops below 1.5V |
Key Features
| Feature | Design Value |
|---|---|
| Dual-mode operation | Supports both continuous DDC1 transmit (VCLK-clocked) and interactive I²C read/write (SCL-clocked) on same SDA line - eliminates need for separate EDID memory and configuration EEPROM |
| Flexible write protection | Two-stage control: VCLK enables writes globally; WP pin adds hardware lock after fuse programming at 7Fh - prevents accidental overwrites during system boot or hot-plug events |
| Page write buffer | Eight-byte internal latch allows burst programming of contiguous addresses without repeated Start/Stop sequences - reduces I²C bus overhead during EDID updates |
| Noise-immune inputs | Schmitt-trigger + 50 ns spike filter on SDA, SCL, and VCLK - ensures robust operation on electrically noisy display interconnects (e.g., VGA, DVI cables) |
| Self-timed write cycle | Internal erase-and-program sequence completes in ≤10 ms - eliminates need for external timing control or polling delay estimation |
Applications
| Monitor EDID Storage | Display Configuration Memory |
|---|---|
Use Scenario: Storing Extended Display Identification Data (EDID) in LCD/LED monitors for plug-and-play video source negotiation. IC Role / Device Role / Timing Role: Primary nonvolatile memory holding standardized display capabilities (resolution, timing, color depth) accessed via DDC1 (VCLK) or DDC2 (I²C) protocol. Use Value: Enables automatic resolution and refresh rate selection by GPU; supports hot-plug detection and dynamic EDID updates without firmware intervention. | Use Scenario: Retaining user-adjusted display settings (brightness, contrast, color balance) across power cycles in smart displays. IC Role / Device Role / Timing Role: Secondary configuration store accessed exclusively in Bidirectional (I²C) mode by display microcontroller during initialization or menu navigation. Use Value: Preserves calibrated settings without requiring battery-backed RAM; leverages same physical device for both EDID and user preferences. |
| DDC Compliance Testing | Embedded Display Interface |
Use Scenario: Validation of DDC1/DDC2 compliance in monitor manufacturing test fixtures using known-good reference EDID content. IC Role / Device Role / Timing Role: Fixed-content memory source emulating standard monitor responses during automated DDC handshake verification. Use Value: Eliminates need for programmable test memory; simplifies fixture design with single pre-programmed 24LCS21AT-I/SN per test station. | Use Scenario: Providing display identity and capability data to embedded systems (e.g., medical imaging panels, industrial HMIs) with integrated graphics controllers. IC Role / Device Role / Timing Role: System-level configuration hub interfacing directly with GPU's DDC engine or custom I²C master for runtime capability queries. Use Value: Reduces BOM count by consolidating display ID and feature flags into one component; supports legacy DDC1 and modern DDC2 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 | Lacks dual-mode capability - supports I²C only (no VCLK or Transmit-Only mode); identical pinout and memory size. | Cannot replace 24LCS21AT-I/SN in DDC1-only systems; suitable only where full I²C control is available and EDID transmission timing is managed externally. | Select only if system uses dedicated I²C master for all EDID reads and does not rely on VCLK-synchronized streaming. |
| AT24C01D-SSHM-T | 1Kbit I²C EEPROM with 1 MHz max clock, but no VCLK input or Transmit-Only mode; different pin 3 function (NC instead of WP). | Requires external logic or firmware to emulate DDC1 behavior; lacks hardware write-protection flexibility of WP+VCLK combination. | Choose when higher-speed I²C access is needed and DDC1 compatibility is not required; verify layout accommodates NC vs. WP pin mapping. |
Compared with 24LC21A-I/SN and AT24C01D-SSHM-T, the 24LCS21AT-I/SN uniquely integrates DDC1-compliant streaming and I²C random access in one device - eliminating external glue logic, reducing PCB area, and enabling seamless transition between legacy and modern display protocols without firmware changes.
Availability
24LCS21AT-I/SN is available at Aetrix Electronics and suitable for monitor manufacturing, display test equipment, embedded HMI development, and industrial panel integration requiring stable component supply and long-lifecycle support.
Supply support for 24LCS21AT-I/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 leading provider of microcontrollers, analog components, and memory solutions, headquartered in Chandler, Arizona, with global design and manufacturing operations.
The 24LCS21A product line was developed specifically for display interface compliance - targeting VESA DDC1/DDC2 standards with dual-mode architecture to simplify EDID implementation in monitors, projectors, and digital signage systems.
FAQ
What is the primary function of the VCLK pin on the 24LCS21AT-I/SN?
The VCLK pin serves as the clock input for Transmit-Only (DDC1) mode, synchronizing sequential EDID bit output on SDA. In Bidirectional (I²C) mode, VCLK must be held high to enable write operations; it is ignored during the self-timed write cycle. The 24LCS21AT-I/SN will not enter Bidirectional mode unless a valid high-to-low transition occurs on SCL while VCLK remains high.
How does write protection work on the 24LCS21AT-I/SN?
Write protection on the 24LCS21AT-I/SN operates in two stages: initially, the device is write-enabled whenever VCLK = high; writing any value to address 7Fh programs an internal fuse, after which both VCLK = high AND WP = high are required for writes. If WP is pulled low, writes are blocked regardless of VCLK state. This dual-control mechanism prevents accidental overwrites during power-up or hot-plug events.
Can the 24LCS21AT-I/SN be used in systems that only support DDC1 and not I²C?
Yes - the 24LCS21AT-I/SN powers up in Transmit-Only (DDC1) mode and continuously streams memory contents (00h–7Fh) on SDA synchronized to VCLK, fully compliant with DDC1 requirements. No I²C master or SCL signal is needed for basic EDID readout. The device remains in this mode unless explicitly triggered into Bidirectional mode via SCL, making it backward-compatible with legacy DDC1-only systems.
What is the maximum clock frequency supported by the 24LCS21AT-I/SN in Bidirectional mode?
The 24LCS21AT-I/SN supports 100 kHz operation down to 2.5V and 400 kHz operation at 4.5V–5.5V in Bidirectional (I²C) mode. AC timing parameters such as THIGH (600 ns min), TLOW (1300 ns min), and TR/TF (300 ns max) are fully specified for fast-mode operation. These values ensure interoperability with standard I²C masters without requiring external timing adjustments.
Does the 24LCS21AT-I/SN require external pull-up resistors on its I²C bus lines?
Yes - the SDA and SCL pins are open-drain, requiring external pull-up resistors to VCC. Recommended values are 10 kΩ for 100 kHz operation and 1 kΩ for 400 kHz operation to meet rise-time specifications (TR ≤ 300 ns at 400 kHz). The 24LCS21AT-I/SN does not integrate internal pull-ups; omitting external resistors will prevent proper I²C bus signaling and mode transition.
24LCS21AT-I/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:
- Not 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:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
24LCS21AT-I/SN FAQ
1.How can I place an order for 24LCS21AT-I/SN through Aetrix?
Please submit a Request for Quotation (RFQ) for 24LCS21AT-I/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 24LCS21AT-I/SN reliable?
The price and inventory of 24LCS21AT-I/SN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 24LCS21AT-I/SN is usually 5 days.
3.What payment methods are accepted for 24LCS21AT-I/SN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 24LCS21AT-I/SN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 24LCS21AT-I/SN?
24LCS21AT-I/SN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 24LCS21AT-I/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 24LCS21AT-I/SN?
For technical support, including 24LCS21AT-I/SN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 24LCS21AT-I/SN requirements.
6.How does Aetrix verify that 24LCS21AT-I/SN is sourced from the original manufacturer or authorized distributors?
All 24LCS21AT-I/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 24LCS21AT-I/SN meets industry standards.
7.What is the process for return or replacement of 24LCS21AT-I/SN?
All 24LCS21AT-I/SN units undergo pre-shipment inspection (PSI). If there is an issue with 24LCS21AT-I/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 24LCS21AT-I/SN part is unused and in its original packaging.
Return procedure for 24LCS21AT-I/SN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
24LCS21AT-I/SN Tags
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