RN42NU-I/RM Equivalent & Substitute Parts

Part Overview

The RN42NU-I/RM is a Bluetooth v2.1 +EDR Class 2 transceiver module manufactured by Microchip Technology, designed for 2.4GHz wireless communication applications. This module features a U.FL connector for external antenna connectivity and operates across a supply voltage range of 3V to 3.6V. The product is currently classified as obsolete, making identification of functionally equivalent alternatives essential for ongoing system support, design updates, and component procurement planning.

Substiute Parts

RN42NU-I/RM

Microchip TechnologyIn Stock: 821RN42NU-I/RM Datasheet

Current PartRFQ

RN4678-V/RM122

Microchip TechnologyIn Stock: 1149RN4678-V/RM122 Datasheet

MFR RecommendedRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the RN42NU-I/RM is determined by the following critical parameters:

RF Compatibility Parameters:

• RF Family/Standard: Bluetooth
• Frequency Band: 2.4GHz
• Protocol Version: Bluetooth v2.1 +EDR or later versions

Electrical Interface Parameters:

• Mounting Type: Surface Mount
• Serial Interface: USB or UART (protocol-compatible alternatives)
• Voltage Supply Range: Compatible with 3V to 3.6V operation or overlapping range

Physical Integration Parameters:

• Package Type: Module form factor
• Antenna Configuration: U.FL connector or integrated antenna solutions

The RN4678-V/RM122 qualifies as a manufacturer-recommended substitute based on shared RF family (Bluetooth), identical frequency band (2.4GHz), surface mount packaging, and module form factor. While this substitute introduces protocol advancement (Bluetooth v5.0) and integrated antenna design, these represent functional enhancements rather than incompatibilities.

Parameter Comparison

Engineering Selection Recommendations

Product Status Consideration: The RN42NU-I/RM is classified as obsolete, while the RN4678-V/RM122 maintains active product status with Microchip Technology. Active status ensures continued availability, technical support, and manufacturing consistency for new designs and production runs.

Compliance & Certification: Both parts maintain ROHS3 compliance and REACH unaffected status, satisfying regulatory requirements for electronic component deployment in regulated markets. The RN4678-V/RM122 carries MSL rating of 1 (Unlimited), compared to the main part's MSL 3 (168 Hours), indicating superior moisture resistance characteristics.

Interface Compatibility: Selection between these parts requires evaluation of host system interface architecture. The main part operates via USB interface, while the substitute employs UART serial communication. System redesign or interface adapter implementation may be necessary depending on existing host controller configuration.

Thermal Operating Range: The RN42NU-I/RM supports extended low-temperature operation (-40°C minimum), while the RN4678-V/RM122 operates from -20°C minimum. Applications requiring sub-zero thermal performance must account for this specification difference.

Antenna Architecture: The main part requires external antenna selection and integration via U.FL connector, while the substitute features integrated chip antenna. This eliminates external antenna procurement and integration complexity but removes antenna customization flexibility.

Frequently Asked Questions (FAQ)

Q: Can the RN4678-V/RM122 directly replace the RN42NU-I/RM in existing designs?

A: Direct replacement requires evaluation of three critical factors: serial interface compatibility (USB vs. UART), antenna architecture (external U.FL vs. integrated chip), and operating temperature range requirements. Physical footprint compatibility must also be confirmed through PCB layout analysis.

Q: What are the key electrical differences between these modules?

A: The substitute part operates at higher supply voltage (3.3V minimum vs. 3V minimum) and exhibits increased transmit current consumption (43mA vs. 30mA). Power output is reduced (1.5dBm vs. 4dBm), though receiver sensitivity is improved (-92dBm vs. -80dBm). These differences impact power budget calculations and link budget analysis.

Q: Does Bluetooth v5.0 in the substitute ensure backward compatibility with Bluetooth v2.1 +EDR devices?

A: Bluetooth v5.0 maintains backward compatibility with earlier Bluetooth versions including v2.1 +EDR through protocol specification design. However, compatibility must be confirmed through application-level testing, as specific feature sets and performance characteristics may differ.

Q: What is the significance of the MSL rating difference?

A: MSL 1 (Unlimited) on the substitute part indicates superior moisture resistance compared to MSL 3 (168 Hours) on the main part. This affects storage conditions, shelf life, and handling procedures. MSL 1 components require less stringent moisture control during manufacturing and assembly processes.

Q: Are there antenna considerations when switching from the main part to the substitute?

A: Yes. The main part requires external antenna selection and U.FL connector integration, providing customization flexibility for specific application requirements. The substitute features integrated chip antenna, eliminating antenna procurement but removing optimization options for particular frequency or directional requirements.

Q: What is the impact of the UART vs. USB interface change?

A: This represents a fundamental host interface change requiring firmware and hardware modifications. UART is a serial protocol requiring different driver implementation compared to USB. Host controller capabilities and existing software architecture must support UART communication protocols.