IoT Fire Alarm Device Design

flux

You should ask Quectel / supplier for the EC25MXGA hardware design package, not just the marketing datasheet.
Ask for:
  1. EC25MXGA Hardware Design Guide
    • Full pin descriptions
    • Power supply requirements
    • PWRKEY / RESET timing
    • UART / USB / SIM / RF reference circuits
    • VDD_SDIO usage guidance
  2. Recommended PCB land pattern / footprint
    • Pad dimensions
    • Pad numbering
    • Paste mask / solder mask recommendations
    • Keepout zones under/around the module
    • Assembly notes
  3. Reference schematic
    • VBAT_RF / VBAT_BB decoupling
    • SIM socket wiring
    • Antenna matching / ESD
    • Status pins
    • Power-on/off sequence
  4. RF layout guidelines
    • 50 Ω antenna routing
    • Ground stitching via recommendations
    • Antenna connector/matching network placement
    • Diversity/GNSS pins if used or unused
  5. Certification documents
    • RCM / ACMA / AS/CA S042 relevance
    • Carrier approval info for Australia
    • LTE band support for AU carriers
    • Test reports if available
  6. Lifecycle / supply confirmation
    • Active production status
    • Recommended replacement if EC25MXGA is not preferred
    • Minimum order / lead time
Short message you can send:
We are designing a dual-modem Australian fire alarm signalling device using 2 × EC25MXGA. Please provide the EC25MXGA hardware design guide, recommended PCB land pattern/footprint, reference schematic, RF layout guide, SIM interface recommendations, VDD_SDIO connection guidance, Australian carrier/certification documentation, and lifecycle/supply status.
D

drewmoutney

Ok I’ll contact them

flux

Good plan. Ask them specifically for the hardware design guide + recommended PCB land pattern for EC25MXGA-128-SNNS.
Until we get that, the safest path is:
  • Keep EC25MXGA in the design.
  • Do not send the PCB to manufacture yet.
  • Continue with placement/routing cleanup only as a draft.
  • Finalize modem footprint, SIM wiring, RF layout, and VDD_SDIO treatment once Quectel confirms the official guidance.
Clean draft layout
Review EC25 wiring
Check power budget
Update factory checklist
Run current checks
Sign up to send

Files

Schematic

Layout

3D View

PCB Outline and Initial Placement Plan
Board setup
  • First-pass board outline: 100 mm × 160 mm rectangle
  • Corners: 2 mm radius
  • Stackup: 4-layer board
    • Layer 1: signals/components
    • Layer 2: ground reference plane
    • Layer 3: power plane
    • Layer 4: signals
Initial placement zones
  • Left edge: 8 FAS input terminals plus power-fail terminal for field wiring.
  • Bottom-left: 12–24 VDC input and protected power-entry stage.
  • Centre: STM32H757 MCU.
  • Right side: Dual EC25 modem modules.
  • Right edge: u.FL/IPEX antenna connectors for external antenna pigtails.
  • Near each modem: One SIM card socket per modem. J4 is modem A SIM; J5 is modem B SIM.
  • Top/front edge: LCD connector and four front-panel buttons.
  • Bottom/service edge: USB-C programming/service and SWD debug connector.
Notes
The placement is a functional first pass only. It is not final manufacturing placement yet. The next layout pass should resolve remaining overlaps, move all passives close to their associated IC pins, and preserve short 50 ohm RF paths from each EC25 ANT_MAIN pin to its u.FL connector.

  • Board setup

  • Initial placement zones

  • Notes