RN42SM-I/RM Equivalent & Substitute Parts

Part Overview

The RN42SM-I/RM is a Bluetooth v2.1 +EDR Class 2 transceiver module manufactured by Microchip Technology, designed for 2.4GHz RF applications with integrated chip antenna. This module is classified as obsolete, making identification of compatible substitute parts essential for ongoing system support and new design implementations. The RN42SM-I/RM provides UART serial interface connectivity with integrated Bluetooth functionality in a surface mount module package.

Substiute Parts

RN42SM-I/RM

Microchip TechnologyIn Stock: 935RN42SM-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 RN42SM-I/RM is determined by the following critical parameters:

Mandatory Compatibility Criteria:

• Manufacturer: Microchip Technology (same manufacturer ensures firmware and protocol compatibility)
• RF Family/Standard: Bluetooth (same wireless standard)
• Frequency: 2.4GHz (same operating frequency band)
• Serial Interface: UART (same communication protocol)
• Antenna Type: Integrated, Chip (same antenna configuration)
• Mounting Type: Surface Mount (same PCB assembly method)
• Voltage Supply: 3.3V compatible range (power supply compatibility)

Performance Parameters (Allowable Variance):

• Protocol version: Bluetooth v5.0 (backward compatible with v2.1 +EDR)
• Data Rate: 1Mbps (lower than original 3Mbps, acceptable for legacy applications)
• Power Output: 1.5dBm (lower than original 2dBm, within acceptable range for Class 2 operation)
• Sensitivity: -92dBm (improved over original -80dBm)
• Current consumption: 37mA receiving, 43mA transmitting (lower than original specifications)
• Operating Temperature: -20°C ~ 70°C (narrower range than original -40°C ~ 85°C)

The RN4678-V/RM122 meets all mandatory compatibility criteria and represents a direct functional substitute with enhanced Bluetooth protocol support and improved power efficiency.

Parameter Comparison

Engineering Selection Recommendations

The RN4678-V/RM122 is the qualified substitute for the obsolete RN42SM-I/RM based on the following engineering criteria:

Product Status Alignment: The RN4678-V/RM122 is actively manufactured by Microchip Technology, ensuring long-term availability and supply chain continuity compared to the obsolete RN42SM-I/RM.

Regulatory Compliance: Both parts maintain ROHS3 compliance and REACH unaffected status, satisfying environmental and regulatory requirements for equivalent component substitution.

Functional Compatibility: The RN4678-V/RM122 maintains identical UART serial interface, 2.4GHz frequency operation, and integrated chip antenna configuration, enabling direct functional replacement in existing system designs.

Protocol Enhancement: Bluetooth v5.0 protocol support in the RN4678-V/RM122 provides backward compatibility with Bluetooth v2.1 +EDR applications while enabling access to enhanced Bluetooth v5.0 features for future development.

Power Efficiency: The RN4678-V/RM122 demonstrates reduced transmit current consumption (43mA versus 65mA), providing improved power efficiency in battery-powered applications.

Operating Temperature Consideration: Applications requiring operation below -20°C or above 70°C must evaluate the narrower operating temperature range of the RN4678-V/RM122 against system requirements.

Frequently Asked Questions (FAQ)

Q: Can the RN4678-V/RM122 directly replace the RN42SM-I/RM in existing designs?

A: Yes. Both modules share identical UART serial interface, 2.4GHz frequency operation, integrated chip antenna, and surface mount configuration. The RN4678-V/RM122 provides Bluetooth v5.0 protocol support with backward compatibility to Bluetooth v2.1 +EDR applications.

Q: What are the key differences in electrical performance?

A: The RN4678-V/RM122 operates at reduced data rate (1Mbps versus 3Mbps), lower power output (1.5dBm versus 2dBm), and improved sensitivity (-92dBm versus -80dBm). Transmit current consumption is reduced from 65mA to 43mA, while receive current remains comparable at 37mA versus 35mA.

Q: Are there voltage supply compatibility concerns?

A: The RN42SM-I/RM requires 3.3V supply. The RN4678-V/RM122 accepts 3.3V to 4.2V supply range. Existing 3.3V power supplies are fully compatible with the substitute part.

Q: What is the impact of the narrower operating temperature range?

A: The RN4678-V/RM122 operates from -20°C to 70°C, compared to the RN42SM-I/RM range of -40°C to 85°C. Applications requiring operation outside the -20°C to 70°C window must evaluate alternative solutions or implement thermal management strategies.

Q: Are firmware or software modifications required for substitution?

A: UART interface compatibility and Bluetooth protocol backward compatibility eliminate the requirement for firmware modifications in most legacy applications. System integration testing is recommended to validate application-specific functionality.

Q: How does Bluetooth v5.0 protocol support affect compatibility?

A: Bluetooth v5.0 is backward compatible with Bluetooth v2.1 +EDR. Existing applications designed for v2.1 +EDR operation function without modification. The v5.0 protocol enables access to enhanced features for new development initiatives.

Q: What packaging differences exist between these modules?

A: The RN42SM-I/RM uses a generic Module package. The RN4678-V/RM122 uses a 33-SMD Module package. Both are surface mount configurations suitable for standard PCB assembly processes.

Q: Is the RN4678-V/RM122 available in production quantities?

A: Yes. The RN4678-V/RM122 maintains active product status with current manufacturing availability, ensuring supply chain continuity for new designs and legacy system support.