Skip to main content
  • Products
  • Evaluate our Software
  • Downloads
  • Free Utilities
  • Purchase
  • Silicon Vendors
  • Support
  • About Us
  • Blog
  • Forum
  • Search
  • Jobs
  • Newsletter
  • Blog
  • Contact
  • Shop
  • Program embedded systems
  • SWD Isolator

    SWD Isolator

    The SWD Isolator can be connected between J-Link or Flasher and any Arm board that uses the standard 20-pin 0.1" male connector to provide electrical isolation.

    Buy now
    Compare Flasher isolators
    Documentation
    Production Tools Icon
    1. 1.Key features
      1. 1.1.Additional features
    2. 2.Connectors and indicators
      1. 2.1.Target connector
    3. 3.Power supply
    4. 4.How to use the SWD Isolator with Flashers
    5. 5.How to use the SWD Isolator with another Arm emulator
    6. 6.Safety

    Overview

    The SWD Isolator can be connected between J-Link or Flasher and any Arm board that uses the standard 20-pin 0.1" male connector to provide electrical isolation. This is essential when the development tools are not connected to the same ground as the application. It is also useful to protect the development tools from electrical spikes that often occur in some applications, such as motor control applications. Another typical field of application is the development of products with sensors or other analog circuitry, in which case the target hardware is protected from electrical noise originating from the development PC.

    SWD Isolator
    SWD Isolator

    Key features

    • 1.2 V to 5 V target operation supported
    • Powered from emulator side
    • Overvoltage and overcurrent protection on emulator side

    Additional features

    • Basic isolation (1 kV DC)
    • Overvoltage protection on VTref pin of target connector
    • Standard 20-pin 0.1" male (target side) and male (emulator side) connector supporting SWCLK, SWDIO, SWO, RESET signals
    • Power consumption on target side: <25 µA
    • SWD frequency: Up to 4 MHz
    • 4 LEDs to indicate emulator power, emulator overload, target power, and target RESET
    • Housing
    • ESD protection

    Connectors and indicators

    The SWD Isolator uses high speed digital isolators that allow a very low propagation time between input and output. It comes with the following connectors and indicators:

    • 20-pin 0.1" male EMULATOR connector 
    • 20-pin 0.1" male TARGET connector
    • Dual color LED (EMULATOR side): Green indicating power, red indicating power overload
    • Dual color LED (TARGET side): Green indicating power, red indicating reset active
    SWD isolator target side pinout
    SWD isolator target side pinout
    SWD Isolator Block Diagram
    SWD Isolator Block Diagram

    Target connector

    The following table shows the target side pinout of the SWD Isolator:

    PinSignalTypeDescription
    1VCCInputThe target side of the isolator draws power over this pin.
    2NCNCThis pin is not connected on the target side of the isolator.
    3NCNCThis pin is not connected on the target side of the isolator.
    5NCNCThis pin is not connected on the target side of the isolator.
    7SWDIOI/OBi-directional data pin of SWD. This pin should be pulled high on the target. Typically connected to SWDIO on target CPU.
    9SWCLKOutputSWD clock signal to target CPU. It is recommended that this pin is pulled to a defined state on the target board. Typically connected to SWCLK on target CPU.
    11NCNCThis pin is not connected on the target side of the isolator.
    13SWOInputSWD data output from target CPU. Typically connected to SWO on target CPU.
    15RESETI/OTarget CPU reset signal. Typically connected to the RESET pin of the target CPU, which is typically called "nRST", "nRESET" or "RESET".
    17NCNCThis pin is not connected on the target side of the isolator.
    19NCNCThis pin is not connected on the target side of the isolator.

    Pins 4, 6, 8, 10, 12, 14, 16, 18, 20 are GND pins connected to GND.

    Power supply

    Both sides, target and emulator, are totally isolated from each other. The emulator side draws power from pin 19. The target side is powered from the emulator via an isolated DC/DC converter.

    How to use the SWD Isolator with Flashers

    In order to use the SWD Isolator, please follow these steps:

    • Connect the SWD Isolator with the Flasher.
    • Power the Flasher.
    • Make sure the green LED on the emulator side is lit. If this is not the case, please enter the command "Power on" in J-Link Commander.
    • Connect the target to the target side of the SWD Isolator.
    • If the target is powered, the green LED on the target side should be lit.

    The red LED on the target side is lit when a Target RESET is active (low).

    How to use the SWD Isolator with another Arm emulator

    The SWD Isolator has been designed for J-Link, but can also be used with other Arm emulators with the same pin-out. In this case, you should make sure that 5 V are supplied to pin 19 of the emulator connector and that your emulator is not damaged when applying 5 V to this pin. Do this at your own risk!

    Safety

    This isolator provides basic isolation only. Do not use with hazardous voltages without further protection measures to avoid risk of electrical shock and fire.

    SEGGER isolators provide a basic isolation to withstand high voltages as mentioned in the resp. technical data section. To preserve integrity of human beings when dealing with potential hazardous voltages it is mandatory to have a second protection measure in place in case the first insulation barrier fails. This is called double or reinforced isolation. How this double isolation can be achieved depends on the use case or application setup. Also check your local safety related directives valid for your country to make sure all requirements are met.


    Suitable products

    • Flasher PRO
    • Flasher PRO XL
    • Flasher Compact
    • Flasher ARM
    • Flasher Portable PLUS
    • Flasher Secure
    • J-Link Pro
    • J-Link ULTRA+
    • J-Link WiFi
    • J-Link PLUS Classic
    • J-Link PLUS Compact
    • J-Link BASE Classic
    • J-Link BASE Compact
    • Online documentation
    • List of downloads
    • Pricing
    • Buy now
    • Regulatory documents

    Headquarters

    SEGGER Microcontroller GmbH

    Ecolab-Allee 5
    40789 Monheim am Rhein, Germany
    info@segger.com
    Tel.: +49-2173-99312-0
    Fax: +49-2173-99312-28

    Locations

    USA: SEGGER Microcontroller Systems LLC

    Boston area
    101 Suffolk Lane
    Gardner, MA 01440, USA
    us-east@segger.com
    Tel.: +1-978-874-0299
    Fax: +1-978-874-0599

    Silicon Valley
    Milpitas, CA 95035, USA
    us-west@segger.com
    Tel.: +1-408-767-4068

    China: SEGGER Microcontroller China Co., Ltd.

    Room 218, Block A, Dahongqiaoguoji
    No. 133 Xiulian Road
    Minhang District, Shanghai 201199, China
    china@segger.com
    Tel.: +86-133-619-907-60

    ISO 9001 certified

    ISO 9001

    30+ years of experience

    First-class embedded software tools since 1992
    • Imprint
    • Disclaimer
    • Code of Conduct
    • Privacy Policy
    © 2025 SEGGER - All rights reserved.