Microchip Technology 24LC22AT-I/SN

Overview

24LC22AT-I/SN from Microchip Technology Inc. is a 2 Kbit dual-mode serial EEPROM designed for VESA DDC/EDID applications in display systems. It operates in Transmit-Only mode (1 Kbit, VCLK-clocked) and Bidirectional I²C mode (2 Kbit, SCL-clocked), supports 2.5–5.5V supply, delivers 1 mA active current, and features 1,000,000 erase/write cycles with >200-year data retention.

For engineers reviewing the 24LC22AT-I/SN datasheet, 24LC22AT-I/SN pinout, 24LC22AT-I/SN application, or 24LC22AT-I/SN equivalent, key selection considerations include its dual-clock interface (VCLK + SCL), E-EDID™ 1.3 compliance, write-protection via VCLK logic level, page-write buffer (8 bytes), and industrial temperature range (–40°C to +85°C).

Technical Context

The 24LC22AT-I/SN implements two independent serial protocols on shared SDA: Transmit-Only mode uses VCLK for unidirectional EDID streaming (address 00h–7Fh), while Bidirectional mode uses SCL for full I²C-compliant read/write access to the entire 256 × 8-bit array. Mode transition requires a valid high-to-low edge on SCL followed by detection of control byte 1010000X.

Its internal architecture includes Schmitt-trigger inputs on SDA, SCL, and VCLK for noise immunity; a self-timed write cycle with auto-erase; and VCC threshold detection disabling programming below 1.5V. Write enable is strictly gated by VCLK = high in Bidirectional mode, enabling hardware-level write protection.

Key Specifications

Pinout & Package

24LC22AT-I/SN is housed in an 8-pin SOIC package (3.90 mm width), RoHS-compliant, with Pb-free matte tin plating. Pin 1 is VSS (ground); pins 2–5 are SDA, SCL, VCLK, and VCC respectively; pins 6–8 are NC (no internal connection).

Key Features

Applications

Equivalent & Alternatives

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

Compared with 24LC22AT-I/SN, the 24LC21AT-I/SN lacks bidirectional capability and firmware update support, while the AT24C02C-SSHM-T requires host-level DDC protocol implementation - making 24LC22AT-I/SN uniquely suited for autonomous, standards-compliant display identification.

Availability

24LC22AT-I/SN is available at Aetrix Electronics and suitable for monitor EDID storage, projector configuration memory, and KVM switch identity modules requiring stable component supply across extended production lifecycles.

Supply support for 24LC22AT-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 U.S.-based semiconductor company specializing in microcontrollers, analog devices, and memory solutions for industrial, automotive, and consumer applications.

The 24LC22AT-I/SN belongs to Microchip's VESA-compliant serial EEPROM product line, engineered specifically for display interface systems requiring autonomous EDID broadcast and field-upgradable configuration storage.

FAQ

What is the primary function of the VCLK pin on the 24LC22AT-I/SN?

The VCLK pin on the 24LC22AT-I/SN 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 functionality enables seamless integration into both legacy and modern display identification architectures without external logic.

Does the 24LC22AT-I/SN support standard I²C addressing, and what is its slave address?

Yes, the 24LC22AT-I/SN supports standard I²C addressing with a fixed 7-bit device code of 1010000 (0x50 in hex). The full 8-bit control byte is 1010000R/W, where R/W = 0 for write and 1 for read. It responds exclusively to this address in Bidirectional mode and generates an ACK only when not executing an internal write cycle - ensuring robust bus arbitration and error detection.

How does the 24LC22AT-I/SN handle mode transitions between Transmit-Only and Bidirectional operation?

The 24LC22AT-I/SN powers up in Transmit-Only mode. A valid high-to-low transition on SCL initiates Transition mode, during which it listens for its control byte (1010000X) on the I²C bus. If detected within 128 VCLK pulses, it enters Bidirectional mode permanently until power cycle. If not detected, it reverts to Transmit-Only mode - providing deterministic, glitch-resistant mode control essential for display enumeration reliability.

What is the maximum page-write size supported by the 24LC22AT-I/SN, and how does it affect memory addressing?

The 24LC22AT-I/SN supports an 8-byte page-write buffer. Page writes are constrained to physical pages aligned to 8-byte boundaries (addresses 00h–07h, 08h–0Fh, etc.). Attempting to cross a boundary causes wraparound within the current page rather than advancing to the next - requiring application firmware to split writes at page edges. This design optimizes I²C bus efficiency while maintaining predictable write timing ≤10 ms per page.

Is the 24LC22AT-I/SN compatible with both 3.3V and 5V I²C buses, and what are the timing implications?

Yes, the 24LC22AT-I/SN operates across 2.5V–5.5V and supports 100 kHz I²C at 2.5V and 400 kHz at 4.5–5.5V. Its Schmitt-trigger inputs and programmable rise/fall time specifications (TR/TF ≤300 ns at 5V) ensure reliable signaling on mixed-voltage buses. Pull-up resistors must be selected accordingly: ~10 kΩ for 100 kHz (3.3V), ~2 kΩ for 400 kHz (5V) - directly impacting bus settling time and noise immunity in real-world display interfaces.