1. BQ25750 design authority: use the latest official TI BQ25750 datasheet, BQ25750EVM User Guide Rev. B / SLUUCY7B, TI BQ25750 schematic/layout checklist, and TI E2E design-file threads as references. The editable EVM CAD files are useful but not mandatory.
2. PoE+ default: use a 12 V isolated IEEE 802.3at PoE+ module as the default intermediate rail.
   • Preferred external BOM target: Silvertel Ag5412 if we want the newer Ag5400 family.
   • Flux-library-available implementation part: Silvertel AG5300, 12 V / 2.5 A isolated PoE module, part UID dde9bf77-ffc7-4620-972a-a0a2d31f62fc.
   • 24 V option: Silvertel Ag5424 if lower secondary-side current is worth the higher downstream voltage stress.
3. LTE default: give the Quectel EM05 its own 3.3 V / 3 A supply branch with local bulk capacitance and controlled power sequencing.
4. GNSS default: keep Mosaic/mini PCIe on a separate clean 3.3 V rail with filtering/load control isolated from LTE burst current.
5. Charging default: configure BQ25750 for 2S Li-ion / 8.4 V regulation, but keep charge current and compensation values provisional until the exact battery pack and TI-derived calculations are complete.

• EVM is a lab evaluation board, not production hardware.
• EVM limits: 55 V max input, 30 V max output, 10 A max charge current.
• EVM defaults include 8 A input current, 10 A output current, and 250 kHz switching frequency.
• EVM has no installed fuse and is not a complete product safety design.
• The carrier design must independently validate FETs, inductor, current sense, compensation, thermal performance, clearances, fusing, reverse-current blocking, and battery safety.

• IEEE 802.3at Type 2 Class 4 PD; backward compatible with 802.3af and usable in 802.3bt environments.
• In compliant PoE+, PSE output may be 30 W but the PD can rely on about 25.5 W available after cable loss before module/downstream losses.
• Ag5412 output: 12 V, 2.5 A, 30 W continuous.
• Ag5424 output: 24 V, 1.25 A, 30 W continuous.
• Isolation: 1500 Vdc input-to-output.
• Efficiency: Ag5412 peak about 93.3%.
• Operating temperature: -40°C to +85°C, but enclosure derating still required.
• Output cap required close to output pins. Ag5412 recommendation: 220 uF minimum, 470 uF typical, 1000 uF max, low ESR suitable for low temperature.
• If an auxiliary/external supply can drive the module output, Silvertel requires a blocking diode or equivalent to prevent output backfeed into the PoE module.

Text
RJ45 / Ethernet magnetics / PoE input
  -> isolated 12 V PoE+ module, default AG5300 in Flux or Ag5412 external BOM target
  -> reverse-current blocking / ideal-diode OR with external DC input
  -> BQ25750 input / direct power-path / 2S charger, provisional until TI checklist complete
  -> downstream rails:
       5V_CM      dedicated CM4 regulator
       3V3_LTE    dedicated 3 A LTE regulator/load switch
       3V3_GNSS   clean GNSS regulator/filter/load switch
       3V3_HUB    USB hub/logic rail
       3V3_AUX    low-current control/peripheral rail

1. Exact Ansmann 2S Li-ion pack datasheet: capacity, max charge current, discharge current, protection status, NTC value/B-constant, connector pinout, certifications.
2. Latest official BQ25750 datasheet revision used for final calculations.
3. TI BQ25750EVM SLUUCY7B and BQ25750 schematic/layout checklist retained as release-review references.
4. Exact Quectel EM05 variant hardware guide: EM05-E, EM05-G, or other regional SKU; verify against the public general guide.
5. Exact Mosaic-X5 / simpleRTK3B mini PCIe electrical and mechanical documentation.
6. Exact PoE module datasheet for chosen module: AG5300 vs Ag5412 vs Ag5424.
7. External DC connector and source specification: nominal/min/max voltage, current limit, surge/transient environment, polarity expectations.
8. Ethernet magnetics / RJ45 / surge-protection part datasheets.
9. USB ESD and SIM ESD protection datasheets.
10. RF connector and antenna/cable datasheets.
11. Enclosure/chassis grounding and mounting constraints.

1. Choose PoE implementation part for schematic: AG5300 now vs create/request Ag5412.
2. Choose intermediate power bus: default 12 V, alternate 24 V.
3. Decide whether rev A supports PoE+ only with charge throttling or adds 802.3bt option for higher charging headroom.
4. Set external DC input nominal/range and whether it should override PoE, share with PoE, or be priority-selected.
5. Define BQ25750 operating mode: standalone resistor programming only, I2C-supervised by CM4, or supervisor MCU controlled.
6. Define battery charge current limit under PoE+ and under external DC.
7. Select NTC topology and connector pinout once battery pack is known.
8. Decide whether to include a fuel gauge in rev A.
9. Decide LTE modem exact region/variant and whether eSIM is required.
10. Decide whether LTE and GNSS supplies need independent load switches under watchdog/supervisor control.
11. Define chassis/earth strategy for PoE isolation, Ethernet shield, USB shields, RF shields, and TVS returns.
12. Define manufacturing target footprints and JLCPCB availability for the chosen PoE module and protection parts.

1. Implement PoE+ input using AG5300 from the Flux library unless user chooses to wait for Ag5412 symbol creation.
2. Add external DC input block and ideal-diode/reverse-current blocking so PoE and DC cannot backfeed each other.
3. Add dedicated 3V3_LTE regulator/load switch with EM05-required bulk/MLCC/TVS/passive footprints.
4. Add dedicated 3V3_GNSS clean rail regulator/filter/load switch.
5. Leave BQ25750 power stage marked provisional until final component values are checked against TI datasheet/checklist and battery data.