24LC21/SN

Memory IC Overview

The Microchip Technology 24LC21/SN is a 1Kb (128 x 8) 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. The device features two operational modes: Transmit-only for monitor identification and Bidirectional mode for standard read/write access. It ensures 1,000,000 erase/write cycles with data retention exceeding 200 years.

Memory IC Feature Summary

• Implements DDC1/DDC2 interface protocols for monitor identification
• Supports dual operation modes including Transmit-only and Bidirectional
• Includes hardware write-protect capability via VCLK pin
• Features low-power CMOS technology with typical standby current of 10 µA

Memory IC Applications

• Monitor identification systems requiring DDC compliance
• Configuration and control information storage
• Serial transmission of system settings
• Low-voltage embedded memory applications

Memory IC Procurement Notes

Verify the specific suffix 'SN' confirms the 8-pin SOIC narrow package variant. Confirm the temperature grade matches industrial requirements (-40°C to +85°C). Note that this component is not recommended for new designs; verify if the updated 24LCS21A is required for long-term availability.

Memory IC Selection Notes

Select this part for legacy designs requiring strict DDC1/DDC2 compatibility. Ensure the application can utilize the unique VCLK pin for mode switching or write protection. Consider the 24LCS21A as a modern alternative if new design rules prohibit obsolete components.

Memory IC Part Context

The 24LC21 belongs to the 24LC21 series of 1Kb EEPROMs. It is distinct from newer variants like the 24LCS21A due to its specific dual-mode architecture. The datasheet explicitly states it is not recommended for new designs, indicating a transition to successor technologies within the manufacturer's portfolio.

Memory IC Replacement Considerations

Microchip recommends using the 24LCS21A as a replacement. Verify pinout compatibility and electrical characteristics before substitution.

Memory IC FAQ

How does the device switch between operational modes?

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.

What is the function of the VCLK pin?

In Transmit-only mode, VCLK provides the clock signal. In Bidirectional mode, VCLK acts as a hardware write-protect control pin; holding it high enables writing, while holding it low prevents it.