Professional IC Distribution & Technical Solutions

Manufacturer: BOURNS

Part Number: PWR263S-35-4R00F

#### Specifications:

• Resistance Value: 4.00 Ω
• Tolerance: ±1%
• Power Rating: 35 W
• Termination Style: Solder Lug
• Mounting Type: Chassis Mount
• Temperature Coefficient: ±100 ppm/°C
• Operating Temperature Range: -55°C to +275°C
• Resistance Material: Wirewound
• Package/Case: PWR263

#### Descriptions:

The PWR263S-35-4R00F is a high-power, wirewound resistor from Bourns designed for chassis mounting applications. It offers a precise resistance value of 4.00 Ω with a tight tolerance of ±1%. The resistor is capable of handling up to 35 W of power dissipation and operates reliably across a wide temperature range.

#### Features:

• High power handling (35 W)
• Precision resistance (±1% tolerance)
• Robust wirewound construction
• Solder lug termination for secure connections
• Wide operating temperature range (-55°C to +275°C)
• Suitable for demanding industrial and power applications

# Technical Analysis of the BOURNS PWR263S-35-4R00F Power Resistor

## Practical Application Scenarios

The BOURNS PWR263S-35-4R00F is a high-power, surface-mount resistor designed for demanding applications requiring precision, durability, and efficient heat dissipation. Key use cases include:

• Power Supplies & Converters: The 4Ω resistance and 35W power rating make it suitable for current sensing, voltage division, and load balancing in switch-mode power supplies (SMPS) and DC-DC converters.
• Motor Control Systems: Used in braking circuits and dynamic braking resistors (DBRs) to dissipate excess energy in servo and industrial motor drives.
• Automotive Electronics: Employed in battery management systems (BMS) and electric vehicle (EV) power distribution due to its high-temperature stability and low inductance.
• Industrial Automation: Integrated into PLCs and industrial inverters for surge protection and snubber circuits, where high pulse handling is critical.
• Renewable Energy Systems: Functions in solar inverters and wind turbine controls to manage power dissipation in high-current paths.

## Common Design-Phase Pitfalls and Avoidance Strategies

Thermal Management Challenges

Pitfall: Inadequate heat sinking or improper PCB layout can lead to thermal runaway, reducing lifespan.

Solution:

• Use a thermally conductive PCB material (e.g., FR4 with copper pours).
• Ensure sufficient airflow or attach a heatsink if operating near maximum power ratings.

Mechanical Stress and Solder Joint Reliability

Pitfall: Mechanical stress from thermal cycling can crack solder joints.

Solution:

• Implement stress-relief PCB footprints with rounded pad edges.
• Follow reflow soldering profiles per BOURNS’ datasheet to prevent thermal shock.

Incorrect Derating Practices

Pitfall: Operating at full rated power without derating for ambient temperature.

Solution:

• Derate power dissipation above 70°C per manufacturer guidelines.
• Monitor temperature rise using thermal imaging or embedded sensors.

## Key Technical Considerations for Implementation

1. Electrical Parameters:

• Resistance Tolerance: ±1% ensures precision in current sensing applications.
• Temperature Coefficient (TCR): ±50 ppm/°C minimizes drift in variable environments.

2. PCB Layout Recommendations:

• Place away from heat-sensitive components.
• Use wide traces to minimize parasitic inductance in high-frequency circuits.

3. Environmental Robustness:

• Conformal coating may be necessary in high-humidity or corrosive environments.

By addressing these factors, designers can optimize the PWR263S-35-4R00F’s performance in high-power applications while mitigating reliability risks.