Rev B1 ECN-06 — LTE SIM7672G global modem (draft)¶
Draft — EverTag Station LTE extension only
Proposed BOM change for 232210 and 232211. Not approved. Extension PCB is not in the first production iteration — can land before or with first LTE build.
Implements the ADR §17 follow-up: "SIM7672G (global variant) is a future option for worldwide single-SKU if needed."
What changes¶
Replace regional modem variants with one global module on both LTE extension PCBs:
| Current (A spec) | Proposed (B1) | |
|---|---|---|
| 232210 modem | SIMCom SIM7672E (EU) | SIMCom SIM7672G-LNGV (global) |
| 232211 modem | SIMCom SIM7672NA (US) | Same SIM7672G-LNGV as 232210 |
| PCB layout / Gerbers | Shared 232210 ↔ 232211 | Unchanged — pin-compatible swap |
| Regional articles | Two modem BOM lines | One modem BOM line (sales/regulatory labels may still differ) |
Orderable MPN: SIM7672G-LNGV (LTE only, no GNSS). Do not use SIM7672G-MNGV / -MNSV variants unless GNSS is added to the schematic (it is not today).
Why¶
| Benefit | Detail |
|---|---|
| Single modem SKU | One part to stock, one EMS assembly variant for LTE |
| EU + US from one board | G is a superset of E and NA LTE bands (see below) |
| Same footprint / AT set | SIM7672X family — no layout respin |
| Lifecycle | Fewer regional EOL risks; aligns with SIMCom global Cat-1bis line |
Cost: ~$3–4/module more than SIM7672E at distributor qty (see sourcing discussion in team notes). Often offset by eliminating a second modem SKU.
Band comparison (SIM7672X Hardware Design Guide)¶
Source: SIM7672X Series Hardware Design (Table 2 — module frequency bands), mirrored in repo as Compatible Design Guide V1.02 family docs.
| Band | SIM7672E (today 232210) | SIM7672NA (today 232211) | SIM7672G (proposed) |
|---|---|---|---|
| LTE-FDD B1 | ✓ | — | ✓ |
| B2 / B4 / B12 / B13 / B25 / B26 / B66 / B71 | — | ✓ (US) | ✓ |
| B3 / B7 / B8 / B20 / B28 | ✓ (EU incl. rural B28) | partial | ✓ |
| B5 | ✓ | ✓ | ✓ |
| B14 / B18 / B19 | — | — | ✓ |
| LTE-TDD B34 / B38 / B39 / B40 / B41 | — | — | ✓ |
| GSM 2G fallback | None | None | None |
| GNSS | Optional (not populated) | Optional (not populated) | Optional — use -LNGV without GNSS |
232210 EU coverage: All current E bands remain on G.
232211 US coverage: All NA bands remain on G, plus extras (B71, TDD) not required for US MNOs but harmless.
Circuit impact analysis¶
Analysis against 232210 master spec and SIM7672X hardware design guide (pin map, Table 9 VBAT, Table 54/55 current, RF §4, GNSS §3.10).
No schematic or layout change required¶
| Block | Part(s) | Verdict | Rationale |
|---|---|---|---|
| Modem footprint | SIM7672G-LNGV | ✅ Drop-in | Same 24×24 mm LCC+LGA, same 124-pin map as E/NA |
| VBAT power | MIC29302, bulk caps | ✅ Unchanged | VBAT 3.4–4.2 V, typ 3.8 V; same ≥2 A peak budget (Table 55) |
| 1.8 V I/O | TXB0106, VDD_EXT pin 15 | ✅ Unchanged | All UART/GPIO/STATUS/NETLIGHT still 1.8 V |
| PWRKEY / RESET | BSS138 × 2 | ✅ Unchanged | Still VBAT domain (pins 1, 16/38) |
| USB_BOOT | Pin 6 NC / pull-up | ✅ Unchanged | Same strapping rules |
| SIM interface | GCT SIM8075, PRTR5V0U2X | ✅ Unchanged | 1.8 V / 3 V SIM — module-controlled |
| B2B connectors | Samtec SFM × 2 | ✅ Unchanged | Signal names and voltages unchanged |
| 232203 base PCB | ESP32 UART/GPIO | ✅ Unchanged | Same B2B pin map |
| Level shifter channels | TXB0106 | ✅ Unchanged | Same six signals |
| NETLIGHT LED (DNP) | 0402 + 1k | ✅ Unchanged | Still 1.8 V push-pull |
| GNSS nets | Pins 40, 90, 95–98, 111, 114–116 | ✅ Stay NC | -LNGV has no external GNSS antenna; leave unconnected per current design |
Verify in prototype — same parts, wider RF scope¶
| Block | Part(s) | Verdict | Action |
|---|---|---|---|
| RF trace + matching | π-network 0402, 50 Ω to RF_ANT (pin 60) | ⚠️ Re-tune | Same topology; VNA tune for additional bands (US B12/B13, TDD B41 near WiFi) |
| Chip antenna | Quectel YC0001CA | ⚠️ Re-characterise | Freq spec already 698–960 MHz / 1710–2700 MHz — covers all G bands; measure TRP/return loss on EU + US bands |
| U.FL fallback | 0 Ω selector (DNP prod) | ⚠️ Same | Keep for B28 marginal / US field trials |
| Ground plane | B2B-L GND bridge | ⚠️ Same | B28 still marginal at ~86 mm effective counterpoise — unchanged risk |
| LTE_TX_BLANK | B2B pin 10 → modem GPIO | ⚠️ Same | Resolve GPIO via AT+CGFUNC at bring-up (modem firmware, not variant-specific) |
| WiFi/LTE coexistence | ESP32 + blanking | ⚠️ Stricter test | B41 (2496–2690 MHz) and B7 sit adjacent to WiFi 2.4 GHz — run coex matrix with G registering US + EU bands |
Not a hardware change — product / firmware / cert¶
| Area | Impact |
|---|---|
| Firmware | esp_modem model string → SIM7672G; band selection still automatic from SIM/PLMN — update gateway LTE docs |
| CE / FCC modular | End-product cert must cover broader band set even if sold in one region |
| Verizon B13 | Module FCC-certified; Verizon Open Development still separate if B13 required — can disable via AT+CBANDCFG |
| Silkscreen | May keep "LTE EU" / "LTE US" article labels on 232210/232211; BOM modem line is common |
| Sales articles | 232505 EU / US subassemblies may share one populated extension PCB |
Power and thermal — datasheet check¶
From SIM7672X Hardware Design Table 55 (VBAT = 3.8 V, GNSS off):
| Mode | Typical current | Design headroom |
|---|---|---|
| Sleep DRX 1.28 s | 700 µA | Unchanged vs E |
| Sleep DRX 0.32 s | 1.5 mA | Unchanged vs E |
| LTE TX (examples) | B20 ~550 mA, B7 ~687 mA, B13 ~484 mA, B41 ~302 mA | All < 2 A LDO / B2B budget |
Conclusion: MIC29302 (3 A), 2× 22 µF + 100 µF tant on VBAT, and ≥ 3 mm VBAT traces remain adequate. No power-component upgrades.
GNSS variant trap¶
SIM7672G is offered with optional GNSS (-MNGV, -MNSV, etc.). Those variants expose GNSS_ANT (pin 90) and GNSS power/UART pins.
| Variant | Use in EverTag? |
|---|---|
| SIM7672G-LNGV | ✅ Yes — LTE only, matches current NC GNSS pins |
| SIM7672G-MNGV / -MNSV | ❌ No — would require GNSS antenna, backup cap on pin 116, and layout not present today |
Scope¶
| Item | B1 change |
|---|---|
| 232210 | Modem BOM: SIM7672E → SIM7672G-LNGV |
| 232211 | Modem BOM: SIM7672NA → SIM7672G-LNGV (same as 232210) |
| 232203 base | No change |
| Enclosure 232506 | No change |
| Connectivity modules 232200–232204 | Out of scope |
Open items¶
| # | Question | Owner | Status |
|---|---|---|---|
| 1 | Confirm SIM7672G-LNGV availability and 1k+ price with SIMCom / Texim / TME |
HW + procurement | Pending |
| 2 | Retune RF matching for US bands + document TRP on B12/B13/B28 | RF / HW | Pending |
| 3 | Coexistence test plan: WiFi + LTE on B41/B7 with chip antenna layout | FW + HW | Pending |
| 4 | Keep two article numbers (232210/232211) for regulatory labels, or merge to one LTE PCB article? | Product + HW | Pending |
| 5 | Update modular integration / FCC exhibits for G module ID | Cert lead | Pending |
| 6 | Verizon B13: required at launch or disable in firmware? | Product | Pending |
Implementation plan (after approval)¶
- This proposal — design review sign-off.
- 232210 index.md — modem §3.1, block diagram, band tables, sourcing §5.1 → SIM7672G-LNGV; note global single-SKU.
- 232211 index.md — delta: same modem as 232210; remove separate NA modem spec.
- Firmware — gateway-wifi.md LTE model string and test checklist (EU + US SIMs on same hardware).
- Certification — modular-integration.md, lab test plan band list.
- ADR §17 — add one-line note that B1 adopts SIM7672G (optional doc pass).
- Prototype — RF tune + coex + multi-carrier SIM matrix on one extension PCB build.
Approval¶
| Role | Name | Decision | Date |
|---|---|---|---|
| HW lead | ☐ Approve ☐ Revise | ||
| RF / cert | ☐ Approve ☐ Revise | ||
| FW engineer | ☐ Approve ☐ Revise | ||
| Procurement | ☐ Approve ☐ Revise |
Related¶
- 232210 Ext LTE EU — master LTE extension spec
- 232211 Ext LTE US — US delta (today: modem only)
- ADR §17 — LTE module decision
- SIM7672X Compatible Design Guide
- SIM7672X Sleep Mode Application Note
- Rev B1 ECN-01 — GPIO remap — unrelated to LTE; same B1 program timeline if desired