SEGGER 5V Target Supply Adapter

What it is

Compact inline adapter that injects a regulated 5 V supply into the standard 20‑pin ARM/JTAG ribbon, preserving a 1:1 pass‑through for all debug signals while powering the target from pin 19.

Where it fits

Plugs directly between any compatible SEGGER J‑Link or Flasher and the 20‑pin ribbon cable, adding a fixed 5 V target supply without extra wiring or bench supplies.

Key specifications

Actual available current depends on the driving probe’s power capability; a typical J‑Link providing ~4.5 V/300 mA supports about 220 mA at 5 V.

Wiring quick‑start

1. Power down the target and disconnect any existing target supply sources to avoid back‑feeding.
2. Insert the adapter between the J‑Link/Flasher and the 20‑pin ribbon (socket to probe, header to cable).
3. Connect the ribbon to the target’s 20‑pin ARM/JTAG header, ensuring pin‑1 orientation.
4. Power the J‑Link/Flasher; the adapter will ramp 5 V to the target within 2–6 ms on pin 19.
5. Verify target current draw stays within the host’s limit (typ. ~220 mA via standard J‑Link).

20‑pin ARM/JTAG pinout (adapter preserves 1:1 signals)

1: VTref 2: GND 3: nTRST 4: GND 5: TDI 6: GND 7: TMS/SWDIO 8: GND 9: TCK/SWCLK 10: GND 11: RTCK 12: GND 13: TDO/SWO 14: GND 15: nRESET 16: GND 17: DBGRQ 18: GND 19: +5V OUT 20: GND 

The adapter drives +5 V on pin 19; all other pins are pass‑through for standard JTAG/SWD signalling per ARM 20‑pin assignment.

Notes and cautions

• Do not parallel external supplies; power the target either from the adapter or an external regulator, not both.
• Large input capacitance above 220 µF may affect ramp behaviour or trip host limits.
• Output voltage can be altered by resistor changes at user risk; use SEGGER’s adjustable adapter (8.06.18) if routinely needing 0.8–3.6 V.