24LC21T/SN

Memory IC Overview

The Microchip Technology 24LC21T/SN is a 128 x 8 bit 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 low-power CMOS technology, ensuring data retention exceeding 200 years and endurance of 1,000,000 erase/write cycles.

Memory IC Feature Summary

• Implements dual operation modes: Transmit-only for monitor identification and Bidirectional mode for standard read/write access.
• Includes hardware write-protect capability via the VCLK pin to prevent unintended memory modifications.
• Features self-timed write cycles with auto-erase and an 8-byte page-write buffer for efficient data handling.

Memory IC Applications

• Monitor identification systems requiring DDC1/DDC2 interface compliance
• Storage of configuration and control information in electronic devices
• Serial transmission of system parameters in bidirectional communication protocols

Memory IC Procurement Notes

Verify that the specific ordering suffix matches the required temperature range and package variant. Confirm compatibility with existing system voltage levels, as the device requires a minimum of 2.5V. Ensure design reviews account for the 'Not recommended for new designs' status by evaluating the successor 24LCS21A for future projects.

Memory IC Selection Notes

Select this component when legacy support for the specific dual-mode protocol (Transmit-only and Bidirectional) is mandatory. The SOIC package suits surface-mount applications. Consider the industrial temperature range availability if operating environments exceed commercial limits. Evaluate power consumption requirements against the specified standby and active current values.

Memory IC Part Context

This EEPROM belongs to the 24LC21 series, designed for applications needing non-volatile storage with specific serial interface requirements. It serves as a specialized solution for monitor identification and control data storage where dual-mode operation provides distinct advantages over standard I2C devices.

Memory IC Replacement Considerations

Microchip recommends using the 24LCS21A instead of the 24LC21 for new designs due to the latter being obsolete.

Memory IC FAQ

How does the device switch between its two modes of operation?

The device powers up in Transmit-only mode. It switches to Bidirectional mode upon detecting a valid high-to-low transition on the SCL pin. Power cycling is required to return to Transmit-only mode.

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

In Bidirectional mode, the VCLK pin acts as a hardware write-protect control. Holding it high enables normal write operations, while holding it low prevents writing to any memory location.