24LCS21A-I/SN

Memory IC Overview

The Microchip Technology 24LCS21A-I/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 at 5V or 100 kHz at 2.5V. The device features a hardware write-protect pin, a page-write buffer for eight bytes, and ensures 1,000,000 erase/write cycles with data retention exceeding 200 years. It functions within an industrial temperature range of -40°C to +85°C.

Memory IC Feature Summary

• Implements DDC1/DDC2 interface standards for monitor identification with automatic recovery to DDC1 mode
• Supports dual operation modes including Transmit-Only and Bidirectional I²C communication
• Includes hardware write-protect functionality via dedicated pin and internal control fuse

Memory IC Applications

• Monitor identification and configuration storage
• Display Power-on EDID transmission
• Serial transmission of control information

Memory IC Procurement Notes

Verify the specific suffix 'I' confirms the industrial temperature range of -40°C to +85°C rather than commercial limits. Confirm the '/SN' designation matches the required 8-pin SOIC plastic package dimensions. Ensure the component meets Pb-free and RoHS compliance requirements as specified in the datasheet revision history.

Memory IC Selection Notes

Select this component when dual-mode operation between continuous EDID transmission and standard I²C read/write access is required. The device is suitable for applications needing flexible write protection through both hardware pins and internal memory fuses. Consider the low standby current and high endurance specifications for long-term deployment in display systems.

Memory IC Part Context

This part belongs to the 24LCS21A series of dual-mode I²C serial EEPROMs manufactured by Microchip Technology. It is designed specifically for Display Data Channel (DDC) applications, allowing seamless transition between transmitting-only mode for EDID data and bidirectional mode for system configuration updates.

Memory IC Replacement Considerations

The 24LC21A serves as a functional substitute but lacks the complete DDC1/DDC2 implementation and recovery logic found in the 24LCS21A. Verify that any replacement maintains the necessary dual-mode capabilities if monitor identification is a critical requirement.

Memory IC FAQ

How does the device switch between Transmit-Only and Bidirectional modes?

The device powers up in Transmit-Only mode. A valid high-to-low transition on the SCL pin triggers Transition mode, where it searches for a valid I²C control byte. If detected, it switches permanently to Bidirectional mode until power is removed.

What is the function of the VCLK pin in Bidirectional mode?

In Bidirectional mode, the VCLK pin acts as a write-enable control. Holding VCLK high allows normal write operations, while setting it low prevents writing to the memory array, effectively acting as a software-controlled write protect.