New Industry Products

Bourns Unveils Isolation Transformers for Serial Communications

September 23, 2021 by Gary Elinoff

The new push-pull transformers are readily compatible with industry leading transformer drivers.

Bourns’ Model PAD00x-T764 Isolation Transformer Series offers functional isolation and is purposed to providing isolated power and to assuring serial communication signal integrity in RS-485, RS-422, RS-232, SPI, I2C, and CAN applications as well as for lower power LAN-based designs.

PAD00x-T764 electrical schematic. Image courtesy of Bourns


The members of Bourns’ Model PAD00x-T764 provide a 3.1 kVAC isolation barrier from high voltage hazards between separate parts of an overall system. The devices are constructed with ferrite toroid cores for the purpose of ensuring both a high coupling factor and heightened efficiency. The windings of the transformers’ coils were designed with an eye towards reduced emissions for better EMI performance.


Compatible with Industry Standard Transformer Drivers

The new transformers are designed to be compatible with standard transformer drivers such as the Maxim MAX253 and MAX845, the Texas Instruments SN6501 and SN6506B,  Analog Devices ADM2485, and other popular transformer drivers.

Simplified diagram of a Texas Instruments SN6501-Q1 transformer driver interfacing through an isolation transformer. Image courtesy of Texas Instruments

PAD00x-T764 series is designed to accept inputs varying over 3.3 to 5 volts, with outputs spanning an industry-standard 3.3 to 10-volt range. Outputs are as high as 250 mA. The company points out that its Bourns Magnetics product line can also support most customization requests and modifications for this series of push-pull transformers.


The Need for Voltage Isolation in Serial Communication Applications

The PAD00x-T764 series was devised for the purpose of maintaining solid communication between subsystems while also providing the necessary isolation between systems. The high withstanding voltage of 3.1 kVAC provides an isolation barrier from high voltage hazards, such as high voltage batteries.

As described by Glenn Roemer, Application Engineer for Custom Magnetics at Bourns, “Serial communication between electronic systems is becoming more widely adopted, and isolating this serial communication is vital to maintaining proper operation of systems that use CAN, RS-485, RS-422, RS-232, SPI, I2C, and low powered LAN communication. The Bourns® PAD00x-T764 isolation transformer series offers a simplified solution that helps maintain proper serial communication while providing the necessary isolation between systems".


The Members of the PAD00x-T764 Series

The four members of this series of transformers all feature the following specifications:

  • Primary Inductance at 100kHz/0.1V is 475µH (±10%)
  • Primary Volt Microseconds (V-µS) is 11
  • Primary DC resistance is a maximum of 650Ω


Features specific to each of the four separate transformers:

  Turns ratio, primary to secondary Secondary DC resistance (maximum)
PAD001-T764117S 1:1.7 900
PAD001-T764120S 1:2 1000
PAD002-T764111S 1:1.1 700
PAD002-T764113S 1:1.3 800


Complete information is available on the PAD00x-T764 Series datasheet



The PAD00x-T763 series are well suited for applications requiring low DC power including:

  • Isolated RS-485/RS-232 power supplies 
  • Industrial automation
  • AC motor drives
  • System integration
  • Embedded solutions
  • Smart metering
  • Communication PHYs


Physical Concerns

  • The PCB mounted transformers are sized at 7.1mm by 6.56 mm and are 4mm high
  • The units operate over a -40 to +125°C temperature range


Regulatory and Safety

  • Functional insulation for a working voltage of 400 Vrms as per IEC 62368, Material Group III, Pollution Degree 2


Environmental Considerations

  • RoHS compliant
  • Halogen-free


Featured image used courtesy of Bourns