24LC21A/SN

Memory IC Overview

The Microchip Technology 24LC21A/SN is a 128 x 8-bit dual-mode Electrically Erasable PROM housed in an 8-pin SOIC package. It operates on a single supply voltage ranging from 2.5V to 5.5V and supports I2C-compatible 2-wire serial interfaces with clock frequencies up to 400 kHz. The device features a self-timed write cycle, a page-write buffer for eight bytes, and ensures over one million erase/write cycles with data retention exceeding 200 years.

Memory IC Feature Summary

• Implements DDC1/DDC2 interface standards for monitor identification
• Supports Transmit-Only and Bidirectional operational modes
• Includes hardware write protection via the VCLK pin
• Provides ESD protection exceeding 4000V

Memory IC Applications

• Monitor identification and configuration storage
• Storage of control information requiring serial transmission
• Industrial temperature range embedded systems

Memory IC Procurement Notes

Verify that the specific ordering suffix matches the required industrial temperature range (-40°C to +85°C) and package type (SOIC). Confirm RoHS compliance status and ensure the datasheet revision aligns with current design specifications before finalizing procurement orders.

Memory IC Selection Notes

Select this component when dual-mode operation between standard I2C and DDC protocols is necessary. Ensure the application requires a maximum of 1Kbit capacity and can accommodate the specific initialization sequence required to transition from power-up Transmit-Only mode to Bidirectional mode.

Memory IC Part Context

This part belongs to the 24LC21 series of serial EEPROMs manufactured by Microchip Technology. It serves as a direct pin and function compatible replacement for the legacy 24LC21 model while adding support for modern display data channel standards.

Memory IC Replacement Considerations

The 24LC21A is explicitly noted as pin and function compatible with the 24LC21. Designers should verify that existing firmware handles the specific mode transition requirements defined in the updated datasheet.

Memory IC FAQ

How does the device switch from its default power-on state?

Upon power-up, the device enters Transmit-Only mode. It switches to Bidirectional mode upon detecting a valid high-to-low transition on the SCL pin followed by a valid control byte.

What is the role of the VCLK pin during Bidirectional mode?

In Bidirectional mode, the VCLK pin acts as a hardware write-protect control. A logic high level enables write operations, while a logic low level prevents writing to the memory array.