Summary of ISOLATED POWER SUPPLY FOR RS485, RS422, RS232, SPI, I2C AND POWER LAN
This article describes a mini isolated power supply project utilizing the Texas Instruments SN6505A IC. Designed for communication interfaces like CAN, RS-485, and SPI, it converts 5V DC input to symmetrical +/- 5.50 V DC outputs with 500mA load current. The design features ultra-low EMI through slew rate control and spread spectrum clocking, along with built-in protections such as thermal shutdown and soft-start capabilities.
Parts used in the Mini Isolated Power Supply:
- SN6505A IC
- Center-tapped transformer
- N-channel power switches
- Internal Power-MOSFET switches
- Load capacitors
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.
Features
- 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
Applications
- Isolated Power Supply for a 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
Read More: ISOLATED POWER SUPPLY FOR RS485, RS422, RS232, SPI, I2C AND POWER LAN
- What applications does this power supply support?
The supply is designed for CAN, RS-485, RS-422, RS-232, SPI, I2C, Low-Power LAN, and low-noise isolated USB supplies. - How does the project achieve ultra-low noise and EMI?
It uses slew rate control of the output switch voltage and Spread Spectrum Clocking (SSC). - What are the output specifications of this supply?
It provides +/- 5.50 V DC symmetrical outputs with an approximate load current of 500mA. - Can the device start up under heavy loads?
Yes, the device includes two 1-A Power-MOSFET switches to ensure start-up under heavy loads. - Does the IC include protection against overheating?
Yes, the internal protection features include thermal shutdown. - How does the system handle high inrush current during power-up?
The SN6505 includes a soft-start feature that prevents high inrush current when powering up with large load capacitors. - What is the operating temperature range of the device?
The device supports a wide temperature range from –55°C to 125°C. - Does the IC have a mechanism to limit current?
Yes, the device includes a 7 A current-limit feature.
