J-Link OB is an on-board debug probe as part of YOUR eval board.

The J-Link OB (for On-Board) is essentially a microcontroller-based, single-chip, J-Link that goes right on the evaluation board. It is compatible with, and has the same features as, J-Link BASE with reduced, but still great, performance.

The microcontroller that is used as a J-Link OB (on the left side of the evaluation board in the diagram below) has a USB-interface on its left side (facing the host) and a JTAG/SWD + SWO interface on its right side (facing the target device).

All features of J-Link BASE can be used, including download into Flash memory.

Why use a J-Link OB?

J-Link OB turns an evaluation board into a complete evaluation kit!
It adds features such as debug support and download into Flash memory, without adding significant extra cost.
Customers can fully use, test, and debug the target device (typically a microcontroller) right out of the box.
J-Link OB is compatible with most IDEs including Eclipse, GDB-based IDEs, and SEGGER Embedded Studio. For a complete list, please refer to the Supported IDEs page.

Who uses a J-Link OB?

J-Link OB is used on various evaluation boards, by several evaluation board manufacturers, for numerous target devices.



  • Fully compatible with and same features as regular J-Link 
  • Inexpensive solution for complete evaluation kits with debug functionality
  • JTAG, SWD + SWO supported
  • Virtual COM Port (K22-Cortex-M, K22-Cortex-A, STM32F072, SAM3U)
  • Optional disable allows use of other external debug probes
  • Compatible with most IDEs 
  • Very small form factor
  • "Drag-And-Drop" interface for intuitive programming of the target device

Model overview / Supported cores

J-Link OB is essentially a microcontroller with a USB device interface running J-Link firmware. Below is a list of currently available options for J-Link-OB, along with the supported cores and interfaces.

Please note that not every J-Link-OB supports every core and every interface/feature. Other microcontrollers can be supported upon request. If you are looking for a combination that is not yet supported, please get in touch with us.

J-Link OB model OB Device Supported target cores JTAG SWD VCOM
Drag & Drop
SWO speed Interface speed Download performance
J-Link-OB-K22-Cortex-M NXP MK22FN128VLH10 LQFP64 package No external crystal required Cortex-M4 @ 96MHz, 128 KB flash Cortex-M





4 MHz 4 MHz 200 KB/s
J-Link-OB-K22-Cortex-A Cortex-A





J-Link-OB-STM32F072-Cortex-M-128KB ST STM32F072CB UFQFPN48 package No external crystal required Cortex-M0+ @48 MHz, 128 KB flash Cortex-M





250 kHz 2 MHz 100 KB/s
J-Link-OB-STM32F072-Cortex-M-64KB ST STM32F072C8
UFQFPN48 package
No external crystal required
Cortex-M0+ @48 MHz, 64 KB flash





250 kHz 2 MHz 100 KB/s
J-Link-OB-STM32F072-Cortex-A-64KB Cortex-A





J-Link-OB-STM32F103-Cortex-M ST STM32F103TB
VFQFPN36 package
Cortex-M3 @72 MHz, 128 KB flash





4500 kHz 2.25 MHz 150 KB/s
J-Link-OB-STM32F103-Cortex-A Cortex-A





J-Link-OB-SAM3U128 Atmel ATSAM3U2C
LQFP100 package
Hi-Speed USB
Cortex-M3 @96 MHz, 128 KB flash





12000 kHz 3.2 MHz 225 KB/s
Available, but not recommended for new designs
J-Link-OB-SAM7S64 Atmel SAM7S64
LQFP64 package
ARM7 @48 MHz, 64 KB flash





6000 kHz 12 MHz 700 KB/s