RD-186 - Small Split Rail Isolated +/- 5V Generator

Design Description

A very low noise differential power supply for split rail systems requiring +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. This design is a smaller version of RD-171. Design uses smaller components on only one side of a double sided FR4 PCB.

This design provides low noise bias rails for ground referenced analog circuitry (under 2 mV p-p ripple noise up to 1 GHz). 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-186 Reference Design
•	CAD Design Files (source schematic, board layout and gerber files)

Additional Product Resources

	LM5001 - High Voltage Switch Mode Boost, Flyback, Sepic Regulator
	datasheet application notes Webench Online design tools samples

• Very Low Noise, <20 mV P-P
• Fully Isolated Outputs, > 500V
• Small Size
• Wide Input Range 10V - 29V
• Double sided PCB
• 600 KHz Operation

Tags: Split Rail Power Supply, Splitrail, Split-Rail, Differential Bias, Differential Biasing, Virtual Ground, Analog Ground, Ground Referencing, Isolated Power, Floating Power