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Carrier Board Design

The nRF9151 Micro Breakout is designed to be mounted on a carrier or application board. The following notes apply when designing a carrier.

  • Download the official KiCad design files for the nRF9151 Micro Breakout. (link coming soon)
  • Read the Nordic docs for component placement which also apply to carrier board design.

Design guidelines

Key considerations for carrier board design.

General

  • If hand soldering an nRF9151 Micro Breakout to the carrier, ensure sufficient clearance between the castellated edges and adjacent components for soldering iron access.
  • Avoid high-speed routing under the top half of the Micro Breakout (i.e. beneath the U.FL connectors).
  • Where the stackup allows, use a solid ground fill on the top copper layer beneath the Micro Breakout.
  • Unused pins may be left electrically floating; however, for mechanical strength, all castellated pins should be soldered to the carrier.
  • Place the UICC/SIM or eSIM close to the Micro Breakout SIM pins.
  • SWD programming uses SWDCLK and SWDIO, but note that ~RESET, VDD and GND are also required by the programmer.
  • Minimise SWD trace length to ensure robust high-speed programming and debugging.
  • The Micro Breakout includes no ESD protection beyond the nRF9151 SiP's built-in rating. Include ESD protection on the carrier board for exposed GPIO and SIM connections.

Power supply

  • Connect all four GND pins to carrier GND with a low-impedance return path to the power supply.
  • Prefer a solid (direct/flood) pad connection; if excessive thermal sinking causes poor solder joints, use spoked connections instead. This mainly applies to GND pins.
  • Bulk decoupling capacitance across the VDD* and adjacent GND pins is advisable depending on power supply quality. Large ceramics (100 µF, 1206 footprint) are satisfactory.
  • All three power domains (VDD, VDD_GPIO, VDD_GPS) may be supplied from the same rail, provided supply voltage limits are not exceeded — VDD_GPIO should not exceed 3.7 V.
  • Power supply bring-up should follow the correct sequence.
  • VDD may be supplied from a regulated supply (e.g. a 3.3 V buck/boost), but ensure the regulator can supply the peak currents demanded by the nRF9151 SiP — see Nordic's power supply and VDD current documentation.