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


Design files


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.

InputsOutput #1Output #2
  VinMin = 10V    Vout1 = 5V    Vout2 = -5V  
  VinMax = 30V    Iout1 = 0.25A    Iout2 = 0.25A  
  • Very Low Noise, < 20 mVP-P
  • Fully Isolated Outputs, > 500V
  • Small Size
  • Wide Input Range > 10V to 30V
  • Double sided PCB
  • 600 KHz Operation

A fully assembled board has been developed for testing and performance validation only, and is not available for sale.

Design files & products


Includes TI products in the design and potential alternatives.

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Technical documentation

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* User guide ± 5V Isolated, Low Noise Split Rail Generator (0.25A, 2.5W total) User Guide Jan. 27, 2012

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