24LC21-I/P

Memory IC Overview

The Microchip Technology 24LC21-I/P is a 128 x 8 bit Electrically Erasable PROM designed for configuration and control information storage. It features dual operation modes: Transmit-only mode, which outputs memory contents via the VCLK pin, and Bidirectional mode, accessed via SCL for standard I2C read/write operations. The device operates on a single supply voltage ranging from 2.5V to 5.5V. It supports clock frequencies of 100 kHz at 2.5V and 400 kHz at 5V. The Industrial temperature grade (-I) ensures functionality between -40°C and +85°C.

Memory IC Feature Summary

• Implements DDC1/DDC2 interface protocols for monitor identification applications
• Features hardware write protection controlled by the VCLK pin logic level
• Includes an internal address pointer for sequential current address reads
• Utilizes 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 in embedded devices
• Serial transmission of system parameters in bidirectional bus architectures

Memory IC Procurement Notes

Verify that the specific ordering suffix matches the required package type, as the 24LC21 is available in both PDIP and SOIC configurations. Confirm the temperature grade suffix corresponds to the intended operating environment, specifically distinguishing between Commercial (C) and Industrial (I) ranges. Ensure design compatibility with the discontinued status noted in official documentation before finalizing procurement plans.

Memory IC Selection Notes

Select this component when dual-mode operation is required, specifically needing a transmit-only capability alongside standard I2C access. The Industrial variant (-I) is necessary for environments exceeding commercial temperature limits. Designers must account for the VCLK pin's dual role as a clock input for transmit mode and a write-protect control signal in bidirectional mode. Verify power supply stability within the 2.5V to 5.5V range to ensure proper threshold detection.

Memory IC Part Context

The 24LC21 belongs to the 24LC series of serial EEPROMs manufactured by Microchip Technology. Official datasheets indicate this specific part is not recommended for new designs, with the 24LCS21A suggested as a modern alternative. The device utilizes an 8-pin package structure common to the family, sharing functional similarities with other 1K-bit I2C EEPROMs while offering unique dual-mode capabilities.

Memory IC Replacement Considerations

Microchip recommends using the 24LCS21A as a replacement for new designs. Verify pinout compatibility and electrical characteristics before substituting.