24LC21-I/SN

Memory IC Overview

The Microchip Technology 24LC21-I/SN is a 1Kb (128 x 8 bit) Electrically Erasable PROM designed for configuration and control information storage. It features a dual-mode operation: Transmit-only mode for monitor identification via the VCLK pin, and Bidirectional mode compatible with the I²C™ bus using SCL and SDA pins. The device operates on a single supply voltage ranging from 2.5V to 5.5V. It supports clock frequencies of up to 100 kHz at 2.5V and 400 kHz at 5V. The industrial temperature grade (-I) ensures functionality within an ambient temperature range of -40°C to +85°C.

Memory IC Feature Summary

• Implements DDC1/DDC2 interface specifications for monitor identification
• Supports both Transmit-only and Bidirectional operational modes
• Includes hardware write-protect capability via the VCLK pin in Bidirectional mode
• Utilizes low-power CMOS technology with typical standby current of 10 µA

Memory IC Applications

• Monitor identification and EDID storage
• Industrial control systems requiring serial configuration data
• Embedded applications needing non-volatile memory for control information

Memory IC Procurement Notes

Verify that the specific ordering suffix matches the required package type and temperature grade. Confirm that the design intent aligns with the component's dual-mode capabilities, particularly the requirement for a valid high-to-low transition on SCL to switch from Transmit-only to Bidirectional mode. Ensure power supply levels remain within the specified 2.5V to 5.5V range for reliable operation.

Memory IC Selection Notes

Select this component when DDC compliance or dual-mode transmission is required. Note that the datasheet indicates this part is not recommended for new designs; consider the 24LCS21A as a modern alternative if new development is underway. Verify that the application can accommodate the specific initialization procedure involving nine clock cycles on VCLK before data output begins.

Memory IC Part Context

The 24LC21 belongs to the 24LC21 family of 1Kb serial EEPROMs manufactured by Microchip Technology. It is distinct from other variants by its specific implementation of the DDC interface and dual-mode architecture. The 'SN' suffix denotes the 8-lead Plastic Small Outline (SOIC) package with a narrow 150 mil body width, suitable for surface-mount assembly.

Memory IC Replacement Considerations

Public documentation explicitly recommends using the 24LCS21A instead of the 24LC21 for new designs.