24LC21/P

Memory IC Overview

The Microchip Technology 24LC21 is a 128 x 8 bit Electrically Erasable PROM designed for configuration and control information storage. It operates on a single supply voltage ranging from 2.5V to 5.5V. The device features a 2-wire serial interface compatible with the I²C™ bus, supporting clock frequencies of up to 400 kHz at 5V and 100 kHz at 2.5V. It offers two operational modes: Transmit-only mode for unidirectional data streaming and Bidirectional mode for standard read/write operations. Key specifications include a typical active current of 1 mA, standby current of 10 µA at 5.5V, and a page-write buffer for up to 8 bytes.

Memory IC Feature Summary

• Implements DDC1/DDC2 interface protocols for monitor identification applications
• Features dual-mode operation allowing transition from power-up Transmit-only mode to Bidirectional read/write mode
• Includes hardware write-protect capability via the VCLK pin in Bidirectional mode
• Utilizes low-power CMOS technology with self-timed write cycles and auto-erase functionality

Memory IC Applications

• Monitor identification systems requiring DDC compliance
• Configuration and control information storage in electronic devices
• Serial transmission of system parameters in bidirectional communication networks

Memory IC Procurement Notes

Verify that the specific order includes the correct suffix indicating the desired package type (PDIP or SOIC) and temperature range (Commercial or Industrial). Confirm that the design accounts for the device being obsolete for new designs; the datasheet explicitly recommends using the 24LCS21A as a replacement. Ensure procurement sources provide genuine Microchip components to guarantee reliability and adherence to the specified electrical characteristics.

Memory IC Selection Notes

Select this component only if legacy compatibility with DDC1/DDC2 interfaces is required. Note that the device enters Transmit-only mode upon power-up, necessitating specific initialization procedures involving the VCLK pin before switching to Bidirectional mode. Consider the 24LCS21A for new designs as it is the recommended successor. Verify that the application can accommodate the specific timing requirements for mode transitions and acknowledge polling during write cycles.

Memory IC Part Context

The 24LC21 belongs to the 24LC series of serial EEPROMs manufactured by Microchip Technology. It is specifically engineered for applications needing small-capacity non-volatile memory with dual-mode capabilities. The device is available in 8-pin PDIP and SOIC packages. It is important to note that Microchip has designated this part as not recommended for new designs, positioning the 24LCS21A as the modern alternative within their product portfolio.

Memory IC Replacement Considerations

Microchip explicitly recommends using the 24LCS21A instead of the 24LC21 for new designs. The 24LCS21A maintains similar functional characteristics but represents the updated version of this technology.