Jlink V9 Schematic -

While this article focuses on the schematic, the hardware is only half of the story. The J‑Link V9 must be loaded with a compatible . There are two main categories:

Connected to a bidirectional buffer that matches the voltage on the VTref pin. SWCLK/TCK: Buffered for clean signal transmission. jlink v9 schematic

: A double-sided PCB that includes ESD protection, optional USB isolation (using ADUM3160), and switchable 3.3V output. This design has been fabricated and tested by numerous community members. While this article focuses on the schematic, the

If the target board drives a voltage higher than the J-Link expects, the buffers can fail. USB Port Damage: Physical strain on the USB connector. SWCLK/TCK: Buffered for clean signal transmission

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