We are designing a custom battery-powered LoRaWAN sensor node (US915) around the RAK4630-9-SM-I module (IPEX antenna variant), targeting a 10-year deployment on a Li-SOCl2 primary cell. Before releasing our PCB for fabrication, we need to confirm four hardware details we could not find in the datasheet or documentation center:
1. LFXO (32.768 kHz crystal)
Does the RAK4630 include a low-frequency crystal (LFXO) connected to the nRF52840, usable by custom firmware? We need to know whether the RTC can run from the LFXO in System ON sleep, or whether only the internal LFRC is available. Our application depends on accurate long-interval RTC timing for scheduled wake-ups, so the LFXO presence and its accuracy spec (ppm) matter for us.
2. RF_LoRa pad (pin 37) on the -SM-I variant
On the IPEX variant, is pad 37 (RF_LoRa) internally connected in parallel with the IPEX connector? We use the IPEX exclusively and left pin 37 unconnected (No Connect, no copper). If the pad is electrically tied to the RF path, does leaving it unterminated create an open stub affecting the 915 MHz path? What treatment does RAK recommend: leave open, ground it, or remove copper underneath?
3. RF shield can material
What material is the shield can made of (nickel silver / tinplate steel)? Our design places a magnetic angle sensor (AS5600) on the opposite side of the PCB, directly under the module, so we need to know whether the shield is ferromagnetic.
4. Copper keep-out under the module
Is there a copper keep-out requirement under the module body for the -SM-I variant, given it has no on-module antenna?
Module: RAK4630-9-SM-I, US915
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