EM4305 is a low-frequency RFID chip that is often discussed and compared with other LF RFID solutions before purchase. This guide answers the most common questions about EM4305, including its features, differences from other LF RFID chips, compatibility, and how to choose the right solution for your application.

What is the EM4305 RFID Chip
EM4305 is a 125kHz low-frequency (LF) RFID chip developed by EM Microelectronic. It is a read/write RFID chip with programmable EEPROM memory, allowing users to store, modify, and manage identification data based on different application requirements.
Unlike read-only RFID chips that contain fixed identification information, EM4305 provides greater flexibility through data programming. This makes it suitable for RFID solutions where users need customized data storage, reusable identification, or system-specific configurations.
The key characteristics of EM4305 include:
- Frequency: 125kHz LF RFID
- Memory: Programmable EEPROM memory
- Function: Read and write capability
- Application focus: Identification, access control, animal tracking, and custom RFID products
Because of its reliable performance and programmable features, EM4305 is commonly integrated into RFID cards, key fobs, and tags where stable short-range identification is required.
When selecting an EM4305 RFID solution, businesses should consider factors such as reader compatibility, required memory functions, application environment, and whether custom RFID card or tag manufacturing is needed.
What Makes EM4305 Different From Other LF RFID Chips?
One of the main differences between EM4305 and many traditional low-frequency RFID chips is whether the chip supports data writing and rewriting.
LF RFID chips can generally be divided into two categories: read-only RFID chips and read/write RFID chips. Understanding this difference is important because it directly affects how the RFID product can be used after deployment.

Read-Only LF RFID Chips
Read-only RFID chips are programmed with a fixed identification number during manufacturing. Once the ID is written, it cannot be modified.
These chips are suitable for applications that only require simple identification, such as:
- Basic access control
- Simple identification systems
- Low-cost RFID applications
For example, users only need the reader to recognize a unique ID number, without updating or storing additional information.
Read/Write LF RFID Chips
Unlike read-only chips, read/write RFID chips such as EM4305 support data programming and rewriting. This means users can store, update, or customize information based on different application requirements.
For businesses, writable memory provides several practical benefits:
-
Customized identification data
Different cards, tags, or key fobs can be programmed with application-specific information instead of using only a fixed ID. -
Flexible system management
Data can be updated when user information, access permissions, or identification requirements change. -
Reusable RFID products
RFID cards and tags can be reprogrammed for different applications, improving product flexibility. -
More customized solutions
Manufacturers and system integrators can design RFID products based on specific project requirements.
Therefore, the advantage of EM4305 is not only that it can store data, but that its programmable capability provides more possibilities for customized RFID solutions. This is why EM4305 is often selected for applications requiring flexible identification, such as access control, animal identification, RFID key fobs, and custom RFID cards.

EM4305 vs T5577: Which RFID Chip Should You Choose?
EM4305 and T5577 are both 125kHz LF RFID read/write chips, and they are often compared when customers choose programmable RFID solutions.
The main difference is that EM4305 is commonly selected for stable RFID identification applications, while T5577 provides more flexibility for different LF RFID configurations.
EM4305 vs T5577 Comparison
| Feature | EM4305 | T5577 |
| Frequency | 125 kHz | 125 kHz |
| RFID Type | LF RFID | LF RFID |
| Read/Write | Yes | Yes |
| Memory | EEPROM | EEPROM |
| Programming | Supported | Supported |
| Main Advantage | Stable and reliable identification | More flexible programming options |
| Common Applications | Access control, animal ID, RFID cards, key fobs | Access control, flexible LF RFID applications |
Which One Should You Choose?
Choose EM4305 if you need:
- Stable LF RFID performance
- Programmable RFID identification
- Custom RFID cards, key fobs, or tags
- Reliable production applications
Choose T5577 if you need:
- More flexible programming options
- Support for different LF RFID configurations
- More customization during system development
In most standard RFID card and tag applications, both chips can provide reliable performance. The best choice depends on your RFID reader compatibility, application requirements, and required programming flexibility.
EM4305 vs EM4100: What Is the Difference?
When choosing a 125kHz LF RFID chip, EM4305 and EM4100 are two commonly compared options. Both chips operate at the same frequency and are widely used in low-frequency RFID applications, but they are designed for different application requirements.
The main difference between EM4305 and EM4100 is the level of flexibility they provide for RFID system design. EM4100 is mainly used for fixed identification, while EM4305 is designed for applications that require programmable data and more customized RFID solutions.
EM4305 vs EM4100 Comparison
| Feature | EM4305 | EM4100 |
| Frequency | 125 kHz | 125 kHz |
| RFID Type | LF RFID | LF RFID |
| Memory Type | EEPROM | Factory-programmed ID |
| Data Storage | Programmable memory | Fixed identification number |
| Read/Write Capability | Supported | Read-only |
| Data Update | Possible | Not possible |
| Application Focus | Flexible RFID identification | Simple ID recognition |
EM4305: For Applications Requiring More Flexibility
EM4305 is suitable for projects where RFID products need customized data handling or application-specific configurations.
Typical use cases include:
- Custom RFID cards with programmed information
- RFID key fobs requiring flexible encoding
- Identification systems with changing data requirements
- Applications where future updates may be needed
The advantage of EM4305 is that it gives system integrators more options when designing RFID solutions.
EM4100: For Simple Fixed Identification
EM4100 is a traditional 125kHz RFID chip mainly used for applications where only a unique identification number is required.
It is commonly selected for:
- Basic access control
- Simple identification systems
- Cost-sensitive RFID projects
Since the ID is fixed, EM4100 is suitable when the RFID system only needs to recognize a tag or card without modifying stored information.
Is EM4305 Compatible with EM4100 Readers?
After comparing EM4305 and EM4100, many customers ask: Can EM4305 work with an existing EM4100 RFID reader?
The answer is: it depends on the RFID reader and system configuration. Although both chips operate at 125kHz LF RFID frequency, they are not always directly interchangeable.
The main reason is that EM4100 and EM4305 use different data functions. EM4100 is a read-only RFID chip with a fixed identification number, while EM4305 is a programmable read/write chip with EEPROM memory. Therefore, an EM4100 reader may not recognize an EM4305 chip unless it supports the required data format and configuration.
Can EM4305 Replace EM4100?
In some applications, EM4305 can replace EM4100, but compatibility must be confirmed before switching.
EM4305 may work when:
- The RFID reader supports compatible LF RFID formats
- The chip is programmed with the required configuration
- The system can recognize the transmitted data format
Before replacing EM4100 with EM4305, businesses should check:
- RFID reader specifications
- Supported chip formats
- System compatibility through sample testing
For custom EM4305 RFID cards, key fobs, or tags, testing samples with the existing RFID system before mass production is recommended. This helps confirm compatibility and avoid issues during production.

When Should You Choose the EM4305 RFID Chip?
EM4305 is a suitable option for projects that require programmable identification, flexible data management, and reliable 125kHz RFID performance.
Choose EM4305 If You Need:
Writable RFID Memory
EM4305 is a good choice when your RFID application requires data storage beyond a fixed identification number. Its programmable memory allows information to be written and updated according to different project requirements.
Programmable RFID Identification
If your RFID system requires customized identification data or specific encoding configurations, EM4305 provides more flexibility than traditional read-only LF RFID chips.
Customized RFID Cards or Tags
EM4305 can be integrated into different RFID products, including cards, key fobs, and tags. It is suitable for businesses that need customized RFID solutions with specific designs, data programming, or product formats.
Stable LF RFID Performance
For applications that require reliable short-range identification, EM4305 provides stable performance in 125kHz LF RFID environments, making it suitable for access control, identification, and tracking applications.
Custom EM4305 RFID Cards and Tags
For businesses looking for ready-to-use RFID products, EM4305 chips can be integrated into various customized RFID cards, key fobs, and tags based on application requirements.
Custom EM4305 RFID Cards
EM4305 RFID cards are commonly used for:
- PVC RFID cards
- Access control cards
- Employee ID cards
- Membership cards
With custom manufacturing, businesses can choose card materials, printing designs, chip encoding, and data programming based on their project needs.
Custom EM4305 RFID Key Fobs
EM4305 key fobs provide a compact RFID solution for applications requiring convenient identification.
Common options include:
- ABS RFID key fobs
- Waterproof RFID key tags
- Compact RFID identification solutions
They are widely used in access control, membership systems, and other identification applications.
Custom EM4305 RFID Wristbands
For applications requiring wearable RFID products, EM4305 can also be integrated into RFID wristbands.
Typical applications include:
- Event RFID wristbands
- Access control wristbands
- Identification wristbands
RFID Customization Services
When selecting a custom EM4305 RFID product, businesses can customize:
- Custom printing
- Chip encoding
- Data programming
- Product shape and design
- Bulk manufacturing
Working with an experienced RFID manufacturer helps ensure chip compatibility, stable production quality, and reliable performance for different applications.
Conclusion
EM4305 is a programmable 125kHz LF RFID read/write chip designed for applications requiring more flexibility than traditional read-only RFID solutions.
Compared with EM4100, EM4305 provides programmable memory and greater customization options. Compared with T5577, EM4305 is often selected for applications that prioritize stable identification and reliable RFID performance.
When choosing an RFID chip, businesses should consider factors such as application requirements, reader compatibility, required data functions, and product customization needs.

