24LC21A-I/SNG Microchip Integrated Circuit (Small Outline Packages) In Stock
The Microchip 24LC21A-I/SNG is a 1 Kbit (128 × 8-bit) I2C serial EEPROM operating from 2.5 V to 5.5 V with a 400 kHz fast-mode interface. It features dual-mode compatibility for both 5 V and low-voltage systems and is housed in an 8-pin SOIC package for compact PCB layouts.
- Manufacturer
- Microchip
- Package
- Small Outline Packages
- Pin Count
- 8
- Lifecycle
- ACTIVE
- Datasheet
- 24LC21A-I/SNG Datasheet PDF
- Category
- Integrated Circuit
- Temp Range
- -40.0°C to 85.0°C
- RoHS
- Compliant
- Lead Time
- 3–7 business days
- Shipping
- DHL Express · Worldwide
What are the key features of 24LC21A-I/SNG?
- 1 Kbit (128 × 8) I2C EEPROM with 400 kHz fast-mode clock supporting reliable non-volatile data storage
- Wide supply range of 2.5 V to 5.5 V enables dual-mode use across 3.3 V and 5 V systems
- 8-pin SOIC (SNG) package with 1.27 mm pitch simplifies hand and automated PCB assembly
- Self-timed write cycle with built-in page-write buffer up to 8 bytes reduces host controller overhead
- Hardware write-protect pin and software address bits enable flexible multi-device bus sharing
What is 24LC21A-I/SNG used for?
The 24LC21A-I/SNG is ideal for storing configuration parameters, calibration data, and small lookup tables in microcontroller-based designs such as industrial sensors, consumer appliances, and medical monitoring devices. Its 2.5 V minimum supply makes it a practical choice for battery-powered IoT nodes and wearable devices where power rails are constrained, while the standard I2C interface integrates directly with nearly every modern MCU without additional level-translation circuitry.
What are the specifications of 24LC21A-I/SNG?
| Pbfree Code | Yes |
| YTEOL | 5 |
| Additional Feature | 2-WIRE SERIAL INTERFACE |
| Clock Frequency-Max (fCLK) | 0.4MHz |
| JESD-30 Code | R-PDSO-G8 |
| JESD-609 Code | e3 |
| Memory Density | 1024bit |
| Memory IC Type | EEPROM |
| Memory Width | 8 |
| Number of Functions | 1 |
| Number of Words | 128words |
| Number of Words Code | 128 |
| Operating Mode | SYNCHRONOUS |
| Organization | 128X8 |
| Package Body Material | PLASTIC/EPOXY |
| Package Shape | RECTANGULAR |
| Package Style | SMALL OUTLINE |
| Parallel/Serial | SERIAL |
| Peak Reflow Temperature (Cel) | 260 |
| Qualification Status | Not Qualified |
| Serial Bus Type | I2C |
| Supply Voltage-Max (Vsup) | 5.5V |
| Supply Voltage-Min (Vsup) | 2.5V |
| Supply Voltage-Nom (Vsup) | 3V |
| Surface Mount | YES |
| Technology | CMOS |
| Temperature Grade | INDUSTRIAL |
| Terminal Finish | Matte Tin (Sn) |
| Terminal Form | GULL WING |
| Terminal Pitch | 1.27mm |
| Terminal Position | DUAL |
| Time@Peak Reflow Temperature-Max (s) | 40 |
| Write Cycle Time-Max (tWC) | 10ms |
| Package | Small Outline Packages |
Compliance & Regulatory
| RoHS Status | Compliant |
| Lead-Free | Yes (Pb-Free) |
| Moisture Sensitivity Level | MSL 1 |
| ECCN | EAR99 |
| HTS Code | 8542.32.00.51 |
| Country of Origin | Thailand |
Where can I find the 24LC21A-I/SNG datasheet?
24LC21A-I/SNG Datasheet DownloadOfficial datasheet from Microchip
What are equivalent replacements for 24LC21A-I/SNG?
Compatible alternatives and drop-in replacements for 24LC21A-I/SNG:
Frequently Asked Questions
What is the storage capacity and organization of the 24LC21A-I/SNG, and how does page-write mode improve throughput?
The 24LC21A-I/SNG stores 1 Kbit of data organized as 128 bytes (128 × 8 bits). Page-write mode allows the host to send up to 8 bytes in a single I2C transaction before the device internally latches and programs the data, reducing the number of start-stop cycles from 128 to as few as 16 for a full-array write and cutting total programming time significantly compared to byte-at-a-time writes.
How does the 2.5 V minimum supply voltage of the 24LC21A-I/SNG benefit designs using low-dropout regulators or single-cell lithium batteries?
A single lithium-ion cell discharges from 4.2 V down to approximately 2.7 V at end of discharge, and many LDOs targeting 3.3 V rails can droop to 2.5 V under load. The 24LC21A-I/SNG's 2.5 V minimum VCC ensures the EEPROM remains readable and writable throughout the battery's useful discharge curve, preventing data-read failures at low state-of-charge that would occur with a 4.5 V minimum device.
For a design with multiple 24LC21A-I/SNG devices on one I2C bus, how many devices can be addressed and what mechanism controls addressing?
The 24LC21A-I/SNG uses a 3-bit hardware address field (A2, A1, A0 pins), which allows up to 8 devices to share a single I2C bus at the same 7-bit address space (0x50–0x57). Each device's address is set by tying the three address pins high or low, requiring no software configuration and enabling simple expansion of non-volatile storage in 1 Kbit increments up to 8 Kbits total on one bus.
Is the 24LC21A-I/SNG a lower pin-count or lower-cost alternative to the 24LC256 for applications that need only a small amount of EEPROM?
Yes. The 24LC21A-I/SNG stores 1 Kbit versus 256 Kbits in the 24LC256, making it appropriate when only a few dozen bytes of configuration or calibration data need to be retained across power cycles. Both use the same I2C protocol and 2-wire interface, so firmware is largely identical, but the 24LC21A-I/SNG typically costs significantly less per unit and is offered in the same compact 8-pin SOIC footprint, easing a capacity-right-sizing swap without PCB changes.
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