In industrial control, data acquisition, and mixed-signal systems, 1W isolated DC/DC converters are essential for board-level power isolation, eliminating ground loops, and establishing independent power domains. Murata Power Solutions’ NMR and NKA series, in their compact SIP-7 packages, offer a cost-effective and reliable solution.

While visually similar, these series differ significantly in input voltage Rating, output configuration, and isolation rating. Proper selection requires strict attention to input voltage matching, load conditions, and isolation requirements.

This guide compares three representative models — NMR100C, NMR118C, and NKA1209SC — based on parameters and application scenarios to help engineers make the right choice.

Parameter Comparison

Application Analysis

• NMR100C

The NMR100C features 5V input and 5V output. Its primary function is not voltage conversion, but galvanic isolation.

• • Key Applications:

Digital Isolator Power: Supplying the secondary side of ADuM1xxx chips or optocouplers.

Bus Isolation: Protecting RS485 / CAN controllers from ground potential differences.

Ground Loops: Breaking ground loops to suppress common-mode noise.

• • Summary: Low cost and simple structure make it the standard choice for 5V digital logic isolation.
• NMR118C

The NMR118C is designed for 24V industrial systems, stepping down 24V rails directly to an isolated 5V.

• • Key Applications:

Industrial I/O Modules: Powering internal 5V logic from a 24V supply.

Building Automation: Providing local control power from a central 24V bus.

Note: This is an unregulated module. If the 24V industrial bus fluctuates, the output voltage will track these changes proportionally. If downstream circuits (e.g., MCU or ADC) require precise 5V (<5% tolerance), an LDO is recommended at the output of the NMR118C.

• NKA1209SC

The NKA1209SC provides ±9V dual outputs, enabling a single module to power dual-supply op-amps.

• • Key Applications:

Precision Analog Front Ends (AFE): Providing positive and negative rails for Op-Amps to ensure zero-centered signals and maximum dynamic range.

Medical & Instrumentation: The 3kVDC isolation (1-minute test) makes it suitable for high-noise or safety-critical environments.

12V Intermediate Bus: Ideal for systems utilizing a 12V distribution rail.

Note: While 3kV isolation improves withstand capability, always verify specific safety standard compliance (e.g., medical MoPP) for the entire system design.

Design Considerations

• Strict Input Voltage Matching

This series uses fixed input ranges without wide-input capability:

NMR100C works ONLY with 5V input.

NMR118C works ONLY with 24V input.

NKA1209SC works ONLY with 12V input.

Warning: Connecting 24V to a 5V module will cause immediate failure; connecting 5V to a 24V module will result in startup failure.

• Minimum Load Requirement

As unregulated converters, these modules typically require ≥10% rated load to maintain output voltage stability.

Under light load or no-load conditions, output voltage can rise to 120%–140% of the nominal value.

Solution: If the system load is very light, add a bleeder resistor in parallel with the output.

• Pinout Differences

Despite sharing the SIP-7 package, pinouts differ. PCB footprints are not interchangeable:

Single Output (NMR): Pin 4 (-Vout), Pin 6 (+Vout).

Dual Output (NKA): Pin 4 (-Vout), Pin 5 (Common/GND), Pin 6 (+Vout).

Device Summary

WIN SOURCE supplies the full Murata NMR/NKA series of isolated DC/DC converters, covering NMR100C, NMR118C, NKA1209SC, and other specifications. Engineers can quickly complete device selection based on system power architecture and isolation requirements by checking real-time inventory and lead-time information through WIN SOURCE, helping accelerate product development cycles.