E1M-AEN EMC Pre-Compliance Assessment
1 Purpose & Status
The E1M-AEN is a System-on-Module (a component), not finished equipment. Under the EMC Directive (2014/30/EU) and equivalent regimes, EMC compliance is demonstrated on the final host product, not on the module in isolation. This document exists to de-risk that host-level test: it identifies the module's likely emission sources from the design, gives integrators a ready test plan, and will carry Alp Lab's own pre-compliance bench results once measured.
The standards, test plan and emitter risk assessment (Section 4) are derived from the netlist and are complete. The measured emission/immunity results (Section 6) are not predictable — they depend on the host board, cabling and enclosure and can only be obtained on an EMC bench. Those sections are placeholders until a pre-compliance scan is run. This document does not constitute a Declaration of Conformity to the EMC Directive.
This assessment applies to E1M-AEN module hardware revision R3.
2 Applicable Standards
The governing standard is set by the host product's market and class. For an industrial host the generic standards apply; for IT/multimedia, the CISPR 32/35 pair. Both are listed; the integrator selects per their product.
| Aspect | Industrial | IT / multimedia |
|---|---|---|
| Emissions | EN IEC 61000-6-4 | EN 55032 (CISPR 32) |
| Immunity | EN IEC 61000-6-2 | EN 55035 (CISPR 35) |
| Radio (Wi-Fi/BLE, 2.4 GHz) | EN 300 328 + EN 301 489-1 / EN 301 489-17 (RED 2014/53/EU) | same |
| North America | FCC Part 15 B (unintentional) + Part 15.247 (2.4 GHz Wi-Fi / BLE) | same |
The on-module Wi-Fi/BLE radio (BDE-BW3501N, 2.4 GHz) is an intentional radiator. Its modular FCC/ISED/RED approvals are pending (see DS-AEN-001, Regulatory Information). Once granted, the integrator inherits them subject to the module's integration conditions (antenna type/gain, labelling, host-port limits). The unintentional-emitter assessment below excludes the radio's intentional transmissions.
3 Pre-Compliance Test Plan
| Test | Method | Setup notes |
|---|---|---|
| Radiated emissions | CISPR 32 / 61000-6-4, 30 MHz–6 GHz | Upper limit to 6 GHz: internal clocks and Gbit-class MIPI lanes above 108 MHz (CISPR 32 upper-frequency rule), and the 2.4 GHz Wi-Fi/BLE harmonics. Near-field probe scan first, then chamber. |
| Conducted emissions | CISPR 32 / 61000-6-4, 150 kHz–30 MHz | On the 5 V DC input and any host I/O leaving the enclosure; LISN / cap-voltage-probe on the DC rail. |
| ESD immunity | IEC 61000-4-2, ±4 kV contact / ±8 kV air | Exposed connectors / host surfaces; verify SoM survives and recovers. |
| Radiated RF immunity | IEC 61000-4-3, 3 V/m (10 V/m industrial) | Watch the analog/ADC, MIPI and Ethernet paths for upset. |
| EFT / burst | IEC 61000-4-4 | DC power + signal ports. |
| Surge | IEC 61000-4-5 | Host-level on external ports (not module-intrinsic). |
| Conducted RF immunity | IEC 61000-4-6, 3 V (10 V industrial) | Cabled ports. |
4 Emitter Risk Assessment (from netlist)
The following sources are ranked by likely contribution to radiated emissions, derived from the E1M-AEN clock tree and power architecture. This guides where to probe first and where layout/filtering effort pays off.
| Source | Risk | Character & mitigation |
|---|---|---|
| DC-DC switchers (4 × buck: TPS62849, TPS628438, TPS6282533, TPS6282518) | High | Switching fundamental + broadband harmonics on power planes and inductor nodes. The two Wi-Fi-rail bucks run only while Wi-Fi is enabled. Keep hot loops tight; input/output filtering; shield/guard the SW nodes. |
| OSPI memory bus (flash + HyperRAM) | High | Fast wide parallel bus, high edge rate → broadband 100 MHz–1 GHz. Series-termination resistors (present); controlled-impedance routing; minimise stub length. |
| Ethernet: 50 MHz XO + DP83825 PHY | Med-High | Narrowband spurs at 50 MHz and harmonics; differential TX/RX edges. Guard the XO; common-mode chokes / magnetics at the host RJ45. |
| SoC core + 38.4 MHz HFXO | Medium | Core clock harmonics; HFXO fundamental. Decoupling (extensive MLCC present); keep crystal loop tight. |
| MIPI CSI/DSI high-speed lanes | Medium | Gbit-class differential serial; well-contained if matched/length-controlled, but a radiator if stubs/imbalance exist. |
| USB 2.0 (high-speed, 480 Mbit/s) | Low-Med | Edge-rate broadband on D±; common-mode choke at host port. |
| Backlight boost converter (KTD2801, 1 MHz) | Medium | Step-up switch node up to 36 V and LED current loop leaving the module on the backlight pads. Keep the carrier LED return tight; filter or shield the backlight cable; scan with the backlight on. |
| 32.768 kHz RTC | Low | Low frequency, low energy; negligible radiator. |
Highest-leverage targets: the four buck regulators and the OSPI memory bus dominate the broadband risk; the 50 MHz Ethernet clock dominates the narrowband risk. A near-field probe pass over these three areas is the fastest route to an early pre-compliance read before chamber time is booked.
5 Integrator Mitigation Checklist
- Power entry: filter the 5 V input at the host connector (π-filter / ferrite); the module's bulk MLCCs handle local decoupling but not host-cable common mode.
- Ethernet: use a magnetics/MagJack with integrated common-mode chokes; keep the 50 MHz XO away from board edges and connectors.
- Enclosure: a conductive enclosure or shield can over the buck + OSPI region is the single most effective radiated-emissions fix if the near-field scan flags it.
- Cabling: treat every cable leaving the enclosure as an antenna — common-mode chokes on high-speed and power cables.
- Wi-Fi: respect the module's antenna and keep-out integration conditions to retain the modular radio approval.
6 Measured Pre-Compliance Results
Pending bench characterisation. Radiated-emission and conducted-emission limit-line plots, immunity pass/fail, and the margin to the selected class limits are inserted here after a pre-compliance scan on a host-representative fixture. Until then no measured EMC performance is claimed.
7 Limitations
- Module, not product. Formal EMC compliance is the host product's responsibility; this assessment is design-level support, not a DoC.
- Predicted, not measured (§4–5). The risk ranking is analytical; only a bench scan produces compliance evidence (§6).
- Host-dependent. Real emissions depend on the carrier board, cabling, enclosure and software activity — all outside the module.
- Radio handled separately. Intentional Wi-Fi/BLE emissions follow the module's modular RED/FCC/ISED approvals (pending), not this unintentional-emitter assessment.
8 Revision History
| Revision | Changes | Date |
|---|---|---|
| 0.1 |
| June 2026 |
| 0.2 |
| October 2026 |
| 0.3 |
| October 2026 |