Isolated Power Supply for RS485, RS422, RS232, SPI, I2C and Power LAN

Rajkumar Sharma        
Project tested

Mini Isolated Power Supply is designed for CAN, RS-485, RS-422, RS-232, SPI, I2C, Low-Power LAN applications. The power supply provides +/- 5.50 V DC symmetrical outputs with load current 500mA from 5V DC input. The project is built using SN6505A IC from Texas instruments. The SN6505A is a low-noise, low-EMI push-pull transformer driver, specifically designed for small form factor, isolated power supplies. It drives low profile, center-tapped transformers 5 V DC power supply. Ultra-low noise and EMI are achieved by slew rate control of the output switch voltage and through Spread Spectrum Clocking (SSC). The SN6505 consists of an oscillator followed by a gate drive circuit that provides the complementary output signals to drive ground referenced N-channel power switches. The device includes two 1-A Power-MOSFET switches to ensure start-up under heavy loads. The internal protection features include a 1.7A current limiting, under-voltage lockout, thermal shutdown, and break-before-make circuitry. SN6505 includes a soft-start feature that prevents high inrush current during power up with large load capacitors.


  • Input Supply 5V DC
  • Output +/- 5.50 V DC symmetrical outputs
  • Output Current 500mA Approx.
  • Ultra-Low EMI
  • Spread Spectrum Clocking
  • Precision Internal Oscillator Options: 160 kHz (SN6505A)
  • Slew-Rate Control
  • 7 A Current-Limit
  • Low Shutdown Current: <1 μA
  • Thermal Shutdown
  • Wide Temperature Range: –55°C to 125°C
  • Soft Start to reduce In-rush current


  • Isolated Power Supply for CAN, RS-485, RS-422, RS-232, SPI, I2C, Low-Power LAN
  • Low-Noise Isolated USB Supplies
  • Process Control
  • Telecom Supplies
  • Radio Supplies
  • Distributed Supplies
  • Medical Instruments
  • Precision Instruments
  • Low-Noise Filament Supplies


Parts List



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