Introduction to DC-DC Converter Selection

Selecting the right DC-DC converter is critical for the success of your power system design. This guide provides a systematic approach to choosing Recom DC-DC converters based on your specific application requirements.

Step 1: Define Input Requirements

Input Voltage Range

the first step is to determine your input voltage characteristics:
  • Nominal voltage: What is your typical operating voltage?
  • Voltage variation: How much does the input vary?
  • Transient conditions: Are there voltage spikes or sags?
Recom offers two main input range options:
  • 2:1 range: Covers 2:1 ratio (e.g., 9-18V for 12V nominal)
  • 4:1 range: Covers 4:1 ratio (e.g., 9-36V for 12V/24V systems)

Input Source Characteristics

consider your power source:
  • Battery systems: Use 4:1 range for battery voltage variation
  • Regulated DC bus: 2:1 range offers better efficiency
  • Automotive: 4:1 range handles load dump and cold crank

Step 2: Determine Output Requirements

Voltage and Current

Calculate your load requirements:
  • Output voltage needed
  • Maximum output current
  • Total output power (P = V × I)
Add 20-30% margin for reliability and future expansion.

Regulation Requirements

consider load regulation needs:
  • Tight regulation: Choose regulated converters
  • Loose regulation: Unregulated may be acceptable
  • Line regulation: Important for varying input conditions

Step 3: Isolation Requirements

When Isolation is Required

Galvanic isolation is necessary for:
  • Safety-critical applications
  • Breaking ground loops
  • Level shifting between voltage domains
  • Medical equipment (patient safety)
  • Industrial noise immunity

Isolation Voltage Levels

recom offers various isolation levels:
  • 1000VDC: Basic industrial applications
  • 1600VDC: Standard industrial grade
  • 3000VDC: High isolation applications
  • 6000VDC: Maximum isolation for harsh environments

Step 4: Package Selection

SIP (Single In-line Package)

  • Compact vertical design
  • 7-pin or 8-pin configuration
  • Ideal for space-constrained designs
  • Through-hole mounting

DIP (Dual In-line Package)

  • Standard horizontal layout
  • 14-pin to 24-pin options
  • Better thermal performance
  • Easy prototyping and assembly

SMD (Surface Mount Device)

  • Automated assembly compatible
  • Smallest footprint
  • Requires reflow soldering
  • Best for high-volume production

Step 5: Environmental Considerations

Temperature Range

recom converters operate from -40°C to +85°C without derating. Consider:
  • Ambient temperature extremes
  • Self-heating from power dissipation
  • Thermal management requirements

Mechanical Stress

for harsh environments, consider:
  • Vibration resistance
  • Shock resistance
  • Humidity and moisture protection

Step 6: Certification Requirements

Safety Certifications

ensure your application requirements are met:
  • UL/EN/IEC 62368-1: Information technology equipment
  • IEC 60601-1: Medical equipment (2xMOPP)
  • AEC-Q100: Automotive applications

EMC Compliance

Consider electromagnetic compatibility:
  • Conducted emissions
  • Radiated emissions
  • Immunity requirements

Application Examples

Industrial Automation

for PLC power systems:
  • Input: 24VDC nominal (18-36V range)
  • Output: 5V at 1A, isolated
  • Package: SIP for compact design
  • Temperature: -40°C to +85°C
  • Recommended: R05P05S

Medical Equipment

for patient-connected devices:
  • Input: 12VDC from medical-grade supply
  • Output: 5V isolated with 2xMOPP
  • Leakage: <100μA for CF rating
  • Recommended: REM3.5-1205S

Battery-Powered Systems

For 12V battery applications:
  • Input: 9-18V (2:1 range)
  • Output: 3.3V at 500mA
  • Efficiency: Maximize battery life
  • Recommended: R-78E3.3-0.5

Design Checklist

before finalizing your selection:

  • [ ] Input voltage range covers all operating conditions
  • [ ] Output power has 20-30% margin
  • [ ] Isolation level meets safety requirements
  • [ ] Package fits mechanical constraints
  • [ ] Temperature range covers environment
  • [ ] Required certifications are met
  • [ ] Efficiency meets system requirements
  • [ ] External component count is acceptable

Conclusion

proper DC-DC converter selection requires careful consideration of electrical, mechanical, and environmental requirements. Recom's comprehensive product portfolio offers solutions for virtually any application. Contact our FAE team for assistance with your specific design requirements.