RD-171 - ± 5V Isolated, Low Noise Split Rail Generator (0.25A, 2.5W total)

A very low noise differential power supply for split rail systems requiring low noise +5V and -5V (higher or lower voltage is possible). This design is fully isolated and capable of floating to over 500V differential from Vin to Vout (higher is possible). The LM5001 IC is a fully integrated flyback regulator which performs all of the current mode control for tight regulation and transient response. The design is small and uses only one side of a double sided FR4 PCB for components. Smaller IC packages are available so the layout can be further optimized.

This design provides very low noise bias rails for ground referenced analog circuitry (under 20 mV p-p total noise up to 1GHz). The design utilizes a very small size PCB footprint. This approach is ideal for many applications including low noise cable drivers, medical electronics, high fidelity low power audio, and other sensitive circuitry that can benefit from very low noise split rail biasing. Input to output isolation is employed for those applications where the input and output voltages might be at different potentials or when the input voltage travels across cabling which might pickup noise. The floating outputs avoid unwanted ground currents and the potential for additional noise pickup. For those that do not require isolation they can remove the feedback isolation section of the design and use a simple resistor divider for setting the feedback voltage.

•	RD-171 Reference Design Document
•	CAD Design Files (Altium Designer source schematic, BOM and board layout)

Additional Product Resources

Board Photo

• Very Low Noise, < 20 mV_P-P
• Fully Isolated Outputs, > 500V
• Small Size
• Wide Input Range > 10V to 30V
• Double sided PCB
• 600 KHz Operation