Jlink V9 Schematic Jun 2026

: 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)

) on all signal lines leading to the 20-pin connector. These resistors also help suppress signal reflections and ringing on long ribbon cables. 5. LED Status Indicators

The standard V9 schematic follows the 20-pin JTAG connector layout, which is the industry standard for ARM debugging. jlink v9 schematic

Sensing: The probe uses an internal ADC or comparative amplifier to sense the voltage on Pin 1 of the JTAG connector.

One of the most complex parts of the J-Link V9 schematic is how it handles target voltage references ( VRefcap V sub cap R e f end-sub : A Mini-USB or Micro-USB port connects to

The schematic uses specialized bidirectional level-shifting ICs, most notably the 74LVC8T245 or 74AVC4T245 . These chips have two separate power supply pins: VCCAcap V sub cap C cap C cap A end-sub (connected to the J-Link internal 3.3V) and VCCBcap V sub cap C cap C cap B end-sub (connected to the target's VTrefcap V sub cap T r e f end-sub

The J-Link V9 must power its internal circuitry while safely interfacing with target boards that may operate at different voltage levels. USB Power (5V Input) Key signals routed through this connector include: VTref

The J-Link V9 schematic represents a fascinating intersection of professional engineering, community collaboration, and hands-on learning. While SEGGER never intended for their intellectual property to be publicly available, the open-source community’s reverse-engineering efforts have produced detailed, verified, and functional designs that serve as excellent learning resources for embedded systems engineers.

: A Type-C implementation with a Vref/3.3V power switch and indicator LED. This design notably removes the RTCK signal.

Many V9 schematics feature a small bridge or short-circuit cap header allowing you to pass 5V or 3.3V back through the probe to power small test boards directly. 🔌 The 20-Pin JTAG/SWD Interface