If you search GitHub or Chinese hardware forums (like 52arm.com or amobbs.com), you will find several reverse-engineered schematics. While Segger has never officially released the V9 schematic (it is a proprietary trade secret), hobbyists have traced the PCBs.
The JLink V9 schematic appears to be well-designed and suitable for mass production. Here are some observations:
A Low Dropout (LDO) regulator drops the 5V USB power down to a stable 3.3V to power the ATSAM3U MCU and internal logic buffers. Target Power Supply ( VTargetcap V sub cap T a r g e t end-sub
: Senses the target's operating voltage (typically 1.2V to 5V) to adjust signal levels accordingly. TMS/SWDIO and TCK/SWCLK : The primary data and clock lines for debugging. jlink v9 schematic
: External crystal oscillators provide the necessary clock signals for the STM32 microcontroller to maintain high-speed communication (up to 20MHz for JTAG). Key Schematic Components
High-performance, self-resetting overcurrent protection. 2. Core Components of the J-Link V9 Schematic
The J-Link V9 supports target voltages from 1.2V to 5V. The schematic includes a regulator (like the RT9193-3.3) to provide a stable 3.3V for its internal components. A dedicated voltage sense circuit allows the V9 to detect the target's voltage level to ensure compatible signaling. 2.3. USB Interface If you search GitHub or Chinese hardware forums (like 52arm
Disclaimer: This information is for educational purposes. SEGGER J-Link is a registered trademark of SEGGER Microcontroller GmbH. If you'd like, I can provide further information on: Common troubleshooting steps based on the schematic Information on the firmware for the J-Link V9 Let me know what you'd like to dive deeper into! Share public link
: A Mini-USB or Micro-USB port connects to the MCU’s hardware USB peripheral. This section includes essential ESD protection and filtering capacitors to ensure stable communication with the PC. Target Connector : The standard v9 design uses a 20-pin 0.1" IDC connector . Key signals routed through this connector include: VTref (Pin 1)
The VTref signal does more than just set the power domain. It's often sampled by an operational amplifier (op-amp) to intelligently drive the level shifter's VccB pin. This is where many clone designs fall short. They often use a common and cheap op-amp like the . Here are some observations: A Low Dropout (LDO)
This chip handles the heavy lifting—processing USB packets from the PC and translating them into JTAG/SWD protocol signals. B. USB Interface
Overall, the J-Link V9 schematic appears to be a well-designed document that provides a good overview of the hardware components and their connections. While there are some areas for improvement, such as adding more documentation and specific part numbers, the schematic seems to be a solid foundation for the J-Link V9 debug probe. Rating: 8/10.
is a widely used debug probe from Segger, and while its official full hardware schematics are proprietary, community-driven "develop feature" projects often revolve around understanding its core architecture for repairs or clones. J-Link V9 Core Architecture
The target microcontroller might run at 5V, 3.3V, or 1.8V. The J-Link V9 uses a combination of (like the 74LVC2T45 or TXB0108) to bi-directionally shift logic levels without distorting the SWD clock (SWCLK) and data (SWDIO) signals.
The heart of most open-source J-Link V9 designs is an STM32 microcontroller, most commonly the or STM32F205RC . This choice is not accidental:
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