232210 - EverTag Ext LTE EU¶


Article Number	232210
Name	EverTag Extension PCB LTE EU
Base PCB	Connects to 232204 Base Full via board-to-board connector
LTE Modem	SIMCom SIM7672E (LTE Cat-1bis, Qualcomm QCX216)
Region	EU (CE)
Status	Not included in the first PCB iteration

Not in First PCB Iteration

This extension PCB is fully specified but is not included in the first PCB production run. The base platform (232204) and enclosure (232506) are designed to accommodate this board in a future iteration.

1. Overview¶

The 232210 is a small extension PCB that stacks on top of the 232204 base PCB via a board-to-board connector. It carries the LTE modem (SIMCom SIM7672E) for EU market cellular connectivity. The LTE modem enables cloud connectivity as a backup or alternative to WiFi, using Cat-1bis LTE.

Key Features¶

SIMCom SIM7672E LTE Cat-1bis modem (EU bands, including B28 / 700 MHz for rural coverage)
Board-to-board socket connector (Harwin M20) to 232204 base PCB
Nano-SIM (4FF) card holder (on this extension board, accessible from underneath)
On-board SMD chip antenna (Quectel YC0001CA) with matching network -- eliminates cable assembly
U.FL test/fallback connector for RF testing and optional external FPC antenna
3.8V LDO to power modem from 5V B2B rail
1.8V↔3.3V level shifters for UART and control signals (modem I/O is 1.8V)
NETLIGHT development LED (DNP in production)
UART interface to ESP32 on base PCB (AT commands via B2B connector)
Power from 232204 5V rail via B2B connector (2A burst capable)
All components on top side only

2. Block Diagram¶

graph TB
    subgraph base [232204 Base PCB]
        ESP32["ESP32-C5 WROOM<br/>(3.3V logic)"]
        PWR_5V["5V / 2A Rail"]
        B2B_BASE["B2B Header: Harwin M20"]
    end

    subgraph ext [232210 Extension PCB - all components top side]
        B2B_EXT["B2B Socket: Harwin M20"]
        LDO38["3.8V LDO<br/>(from 5V B2B)"]
        LVLSHIFT["1.8V↔3.3V<br/>Level Shifters"]
        MODEM["SIMCom SIM7672E<br/>(1.8V I/O)"]
        SIM["Nano-SIM 4FF Holder"]
        CHIP_ANT["On-Board Chip Antenna<br/>Quectel YC0001CA"]
        UFL["U.FL (test/fallback)"]
        LED_NET["NETLIGHT LED (DNP in prod)"]
    end

    PWR_5V --> B2B_BASE
    ESP32 <-->|"LTE UART + control<br/>(3.3V)"| B2B_BASE
    B2B_BASE <-->|"14-pin B2B"| B2B_EXT

    B2B_EXT -->|"5V"| LDO38
    LDO38 -->|"3.8V VBAT"| MODEM
    B2B_EXT <-->|"3.3V signals"| LVLSHIFT
    LVLSHIFT <-->|"1.8V signals"| MODEM

    MODEM <--> SIM
    MODEM -->|"RF"| CHIP_ANT
    MODEM -.->|"RF (alt)"| UFL
    MODEM -.->|"NETLIGHT<br/>(1.8V)"| LVLSHIFT
    MODEM -.->|"NETLIGHT"| LED_NET

3. Schematics¶

3.1 LTE Modem -- SIMCom SIM7672E¶

Parameter	Value
Manufacturer	SIMCom
Part Number	SIM7672E
Chipset	Qualcomm QCX216
Technology	LTE Cat-1bis (single RX antenna)
Region	EU (CE-RED)
Bands	B1, B3, B7, B8, B20, B28 (EU coverage incl. 700 MHz rural)
Fallback	None (no GSM -- 2G networks sunsetting across EU)
Interface	UART (AT commands), all I/O at 1.8V logic level
Supply	3.4--4.2V (VBAT pins), typical 3.8V
Peak Current	Up to 2A during TX burst
Sleep Current	<1 mA (SLEEP1 mode, DTR high, USB disconnected)
Package	LCC+LGA, 24 x 24 x 2.4 mm

1.8V Logic Level

All SIM7672E UART, GPIO, STATUS, and NETLIGHT pins operate at 1.8V logic (the module provides a VDD_1V8 reference output on pin 15). The ESP32 on the base PCB uses 3.3V logic. Bidirectional level shifters are required on all signals crossing the B2B connector. See section 3.7.

Band 28 (700 MHz) for Rural EU Coverage

The SIM7672E adds Band 28 (700 MHz) compared to the A7672E it replaces. B28 is actively being deployed by Nordic/EU operators (Telia, Tele2/Telenor Net4mobility) for rural and countryside coverage. This is critical for installations in agricultural, forestry, and remote industrial sites. The on-board chip antenna supports 698--960 MHz, covering B28.

Design notes:

Module has internal PMIC -- provide clean 3.8V input (see section 3.6)
Follow SIMCom SIM7672X hardware design guide for decoupling and layout
Keep RF trace to chip antenna short and impedance-controlled (50 ohm)
PWRKEY and RESET pins operate in VBAT voltage domain (3.4--4.2V), not 1.8V -- use open-drain drive from level shifter or NPN transistor from 3.3V ESP32 GPIO
USB_BOOT (pin 6) must not be pulled LOW during power-up (strapping pin, internal pull-up)

3.2 Board-to-Board Connector (Extension Side -- Socket)¶

Mating socket to the Harwin M20-8750742 header on the 232204 base PCB.

Parameter	Value
Connector Family	Harwin M20 series, 2.54mm (0.1") pitch
Part Number	M20-7810745 (2x7, 14-pin, vertical SMT, female, dual entry)
Tape & Reel	M20-7810745R (T&R variant for automated placement)
Stacking Height	~10--11mm PCB-to-PCB (mates with M20-8750742 header)
Current Rating	3A per contact

B2B Pin Assignment (matches 232204 header)¶

Pin	Signal	Direction (ext→base)	Voltage	Notes
1	VIN_5V	Power from base	5V	2A burst for LTE modem TX
2	GND	Power	--	Current return #1
3	GND	Power	--	Current return #2 (doubled for 2A)
4	LTE_UART_TX	ESP32 → modem	3.3V	AT commands from ESP32 (level-shifted to 1.8V on ext board)
5	LTE_UART_RX	modem → ESP32	3.3V	AT responses to ESP32 (level-shifted from 1.8V on ext board)
6	LTE_POWER_KEY	ESP32 → modem	3.3V	Modem power on/off (level-shifted to VBAT domain)
7	LTE_RESET	ESP32 → modem	3.3V	Hardware reset (level-shifted to VBAT domain)
8	LTE_STATUS	modem → ESP32	3.3V	Network registration indicator (level-shifted from 1.8V)
9	NETLIGHT	modem → ESP32	3.3V	Blink pattern decoded by ESP32 for LED2 status (level-shifted from 1.8V)
10	LTE_TX_BLANK	ESP32 → modem	3.3V	WiFi/LTE TX coexistence blanking
11	EXT_DETECT	ext → base (P1.12)	Analog	Extension variant ADC divider
12	Spare	--	--	Reserved for future use
13	Spare	--	--	Reserved for future use
14	Spare	--	--	Reserved for future use

All B2B Signals are 3.3V

Level shifting happens on the extension board, close to the modem. All signals crossing the B2B connector are at 3.3V logic (matching the ESP32 on the base PCB). The base PCB (232204) does not need any level shifting circuitry for the LTE interface.

No SIM or RF Signals on B2B Connector

SIM card and RF coax are both local to this extension board. SIM signals run from the modem directly to the SIM holder (short traces, same PCB). The on-board chip antenna is soldered directly to the extension PCB. Nothing crosses the B2B connector except power, UART, and control/status signals.

3.3 SIM Card Holder¶

Parameter	Value
Type	Nano-SIM (4FF) push-push holder
Location	On this extension PCB (232210), top side, card slot facing downward
Access	SIM card accessible from underneath the extension board
Routing	SIM signals routed locally from modem SIM pins (short traces)

Design notes:

SIM holder mounted on top side of extension board, with the card insertion slot facing downward -- the SIM card is inserted from underneath (same access side as the USB-C connector on the base PCB)
All SIM traces (SIM_CLK, SIM_DATA, SIM_RST, SIM_VCC) are routed locally on the extension PCB between modem and SIM holder -- no B2B routing
ESD protection on all SIM lines (TVS diode array close to SIM holder)
Controlled impedance per ISO/IEC 7816 SIM specification
SIM signals operate at 1.8V or 3.0V (module-controlled) -- no external level shifting needed

3.4 On-Board Chip Antenna (Primary)¶

Parameter	Value
Manufacturer	Quectel
Part Number	YC0001CA
Type	SMD chip monopole antenna (IFA), tape & reel
Frequency	698--960 MHz / 1710--2700 MHz
Peak Efficiency	Up to 72.9%
Dimensions	35 x 8.5 x 3 mm
Mounting	SMD reflow (no cable, no manual assembly)
Impedance	50 ohm (with matching network)
Compliance	RoHS, REACH
Est. Price	~$0.19 @ 500+ (JLCPCB/LCSC)

Assembly Simplification

The on-board chip antenna eliminates the FPC antenna, U.FL coax cable, and manual cable connection step. All antenna assembly is done during standard SMD reflow -- no manual labor required. This is significant for European EMS assembly where labor cost is high.

Design notes:

Place at PCB board edge with the antenna element extending beyond the ground plane
Keep-out zone: No ground plane or copper pour within ~5 mm of the antenna radiating edge. No components within the keep-out zone.
Matching network: 2--3 component pi-network (0402 L/C pads) between modem RF pad and antenna input. Tuned during prototype phase with VNA to compensate for PCB-specific detuning.
Ground plane considerations: Sub-GHz efficiency depends on ground plane length. The extension board + base board (connected via B2B GND pins) provide a combined ground plane. Target >80 mm ground plane length in the antenna axis direction for acceptable B20/B28 performance.
The antenna covers all SIM7672E bands (B1, B3, B7, B8, B20, B28) plus Cat-M/NB-IoT bands for future module flexibility.

3.5 U.FL Test / Fallback Connector¶

Parameter	Value
Type	U.FL or equivalent
Location	On this extension PCB, top side, near modem RF pad
Purpose	RF testing (VNA, spectrum analyser) and optional external FPC antenna fallback
Impedance	50 ohm

Design notes:

Place adjacent to the modem RF pad, between the matching network and the chip antenna
Use a 0 ohm resistor selector (two 0402 pads) to route RF to either the chip antenna (default, populated) or the U.FL connector (DNP by default)
During development: populate U.FL path, connect VNA or spectrum analyser for RF characterisation. Measure antenna efficiency and return loss on all bands.
In production: populate chip antenna path (0R to chip antenna), DNP the U.FL connector
If field testing shows the chip antenna has insufficient rural B20/B28 performance, the design can fall back to an external FPC antenna (Quectel YPCA004AA, $0.50--0.80) via U.FL + cable -- same antenna article 232251 originally planned

3.6 Modem Power Supply (3.8V LDO)¶

The SIM7672E requires a 3.4--4.2V supply (VBAT pins 55--57) with up to 2A burst capability during LTE TX. The B2B connector provides 5V from the base PCB. A dedicated LDO on the extension board converts 5V to 3.8V.

Parameter	Value
Input	5V from B2B connector (VIN_5V, pin 1)
Output	3.8V (typical VBAT for SIM7672E)
Max Current	2A continuous, 2A peak
Dropout	<500 mV at 2A
Suggested IC	TPS7A2020 (TI), or RT9013-38 (Richtek), or similar 3.8V fixed LDO with ≥2A rating

Bulk Capacitance Required

SIMCom requires ≥100 µF (recommended 300 µF) bulk capacitance on VBAT, placed close to the modem power pins. Use a combination of ceramic (22 µF × 2, X5R, 6.3V) and electrolytic/tantalum (100--220 µF, 6.3V) capacitors. VBAT trace width: minimum 3 mm per SIMCom hardware design guide.

Design notes:

Place LDO close to B2B power pins to minimise input trace length
Place bulk capacitors (ceramic + tantalum) close to modem VBAT pins
The LDO must handle 2A transient current during LTE TX bursts -- verify transient response with adequate output capacitance
The SIM7672E VDD_1V8 output (pin 15) provides the 1.8V reference for level shifters -- no external 1.8V regulator needed

3.7 Level Shifters (1.8V ↔ 3.3V)¶

All SIM7672E digital I/O operates at 1.8V logic (power domain: VDD_1V8, pin 15). The ESP32 on the base PCB operates at 3.3V. Bidirectional level shifters are required for all signals crossing the B2B connector.

Signal Group	Signals	Direction	Level Shift
UART data	LTE_UART_TX, LTE_UART_RX	Bidirectional	3.3V ↔ 1.8V
Control	LTE_POWER_KEY, LTE_RESET	3.3V → VBAT (3.8V)	See note below
Status	LTE_STATUS, NETLIGHT	1.8V → 3.3V	Unidirectional
Coex	LTE_TX_BLANK	3.3V → 1.8V	Unidirectional

Suggested level shifter IC: TXB0106 (TI, 6-channel bidirectional, auto-direction-sensing) or TXS0108E (8-channel). Both support 1.2--3.6V on each side. Use VDD_1V8 from modem pin 15 as the low-side supply, and 3.3V from B2B as the high-side supply.

PWRKEY and RESET: VBAT Domain

The SIM7672E PWRKEY (pin 1) and RESET (pin 16) pins operate in the VBAT voltage domain (3.4--4.2V), not 1.8V. These cannot use a standard 1.8V↔3.3V level shifter. Options:

NPN open-drain driver: 3.3V ESP32 GPIO → 10k base resistor → NPN transistor → collector to modem pin with pull-up to VBAT. Active-low drive (ESP32 HIGH = modem pin LOW).
N-channel MOSFET level shifter: BSS138 or equivalent, source to 3.3V side, drain to VBAT side with pull-up.

The PWRKEY requires a >500 ms LOW pulse to toggle power. RESET requires a >100 ms LOW pulse for hard reset. Both are infrequent operations -- simple NPN/MOSFET circuits are sufficient.

3.8 NETLIGHT Development LED¶

Parameter	Value
LED	Green 0402 or 0603 LED + series resistor (1k)
Signal	Taps SIM7672E NETLIGHT pin (push-pull output, 1.8V)
Purpose	Visual LTE registration status during development
Production	DNP (Do Not Populate) once firmware is validated

The NETLIGHT pin outputs a hardware blink pattern indicating network registration state:

Pattern	Meaning
64ms on / 800ms off	Not registered, searching
64ms on / 3000ms off	Registered to network
64ms on / 300ms off	GPRS/data transfer active

The LED taps the NETLIGHT signal before level shifting, directly on the 1.8V side. A 1k series resistor limits current for the 1.8V drive. The same signal is also level-shifted to 3.3V and routed to B2B pin 9 for ESP32 blink-pattern decoding.

Development Aid -- DNP in Production

The NETLIGHT LED and its series resistor are populated during development and prototype builds for visual LTE status verification without requiring firmware. Mark these two components as DNP in the production BOM once LTE status reporting via LED2 is validated in firmware.

3.9 USB_BOOT Strapping (Pin 6)¶

Parameter	Value
Pin	6 (USB_BOOT)
Domain	1.8V
Requirement	Must not be pulled LOW during power-up

The SIM7672E pin 6 (USB_BOOT) is a strapping pin. If pulled LOW during power-up, the module enters USB firmware download mode instead of normal operation. The pin has an internal pull-up. Do not route any signal to this pin -- leave unconnected or add a 10k pull-up to VDD_1V8 for extra safety.

4. Pin-Out¶

Signals are split between the B2B connector (to/from base PCB) and local connections (modem ↔ SIM, modem → antenna).

4.1 B2B Connector Signals¶

See section 3.2 for the full 14-pin assignment. All B2B signals are at 3.3V logic (level shifting to 1.8V/VBAT happens on this extension board). Signals connect to the ESP32 on the 232204 base PCB (not nRF54 directly).

4.2 Local Signals (Extension Board Only)¶

These signals do not cross the B2B connector -- they are routed locally on this extension PCB:

Signal	From	To	Voltage	Notes
SIM_CLK	SIM7672E	SIM holder	1.8/3V	SIM clock (up to 5 MHz)
SIM_DATA	SIM7672E	SIM holder	1.8/3V	SIM data (bidirectional)
SIM_RST	SIM7672E	SIM holder	1.8/3V	SIM reset
SIM_VCC	SIM7672E	SIM holder	1.8/3V	SIM power (from modem internal regulator)
RF_OUT	SIM7672E	Matching network	RF	50 ohm to chip antenna or U.FL (via 0R selector)
NETLIGHT	SIM7672E	LED + level shifter	1.8V	Tapped locally for dev LED, then level-shifted to 3.3V for B2B
VDD_1V8	SIM7672E	Level shifters	1.8V	Module 1.8V reference output (pin 15), supplies low-side of level shifters
VBAT	3.8V LDO	SIM7672E	3.8V	Module power supply (pins 55--57)

5. Component Selection¶

5.1 LTE Modem¶

Parameter	Value
Manufacturer	SIMCom
Part Number	SIM7672E
Chipset	Qualcomm QCX216
Technology	LTE Cat-1bis (no GSM fallback)
Region	EU (CE-RED certified)
Bands	LTE-FDD: B1, B3, B7, B8, B20, B28
Package	LCC+LGA, 24 x 24 x 2.4 mm
Est. Price	~$7--10 @ 1k volume (LCSC/Western distributor)
Datasheet	Compatible Design Guide V1.02, Sleep Mode App Note

Rationale (see also ADR #17):

Band 28 (700 MHz): Adds critical rural EU coverage missing from A7672E (B1/B3/B5/B7/B8/B20 only). B28 is actively deployed by Nordic operators for forests, mountains, and countryside.
Cat-1bis: Single RX antenna (no MIMO diversity required). Sufficient throughput (10/5 Mbps) for MQTT gateway data. Simpler RF design than full Cat-1.
Qualcomm QCX216 chipset: Lower sleep current (<1 mA vs ~3 mA for A7672E's ASR1603). Important for battery-backed gateway operation.
Footprint-compatible: Same 24x24mm LCC+LGA as A7672E. Same AT command set. Pin-compatible for UART, SIM, power, NETLIGHT, STATUS, PWRKEY, RESET.
No GSM fallback: Acceptable trade-off -- EU 2G networks are being shut down (Telia SE 2025, Telenor NO 2025--2026, Vodafone DE 2025).

Alternative modules (evaluate before production):

Module	Category	Key Difference	Footprint
SIM7672G	Cat-1bis	Global bands (incl. B28), LTE-TDD	Same 24x24mm
A7673E	Cat-1bis	ASR1606 chipset, may be cheaper	Same 24x24mm
A7682E	Cat-1	Smaller (19.6x19.6mm)	Different footprint

Supplier Links:

5.2 Board-to-Board Connector (Extension Side -- Socket)¶

Parameter	Value
Manufacturer	Harwin
Part Number	M20-7810745 (tube) or M20-7810745R (tape & reel)
Configuration	2x7 = 14-pin, vertical SMT, female, dual entry
Pitch	2.54mm (0.1")
Height	3.75mm above PCB
Current Rating	3A per contact
Est. Price	~$0.40--0.70

Mates with Harwin M20-8750742 header on 232204 base PCB. Stacking height ~10--11mm.

5.3 SIM Card Holder¶

Parameter	Value
Type	Nano-SIM (4FF) push-push, SMT
Mounting	Top side, card slot facing downward
Est. Price	~$0.30--0.50 USD

Part number TBD by CAD designer. Standard nano-SIM push-push holder with detect switch.

5.4 On-Board Chip Antenna¶

Parameter	Value
Manufacturer	Quectel
Part Number	YC0001CA
Type	SMD chip monopole (tape & reel)
Frequency	698--960 MHz / 1710--2700 MHz
Dimensions	35 x 8.5 x 3 mm
Efficiency	Up to 72.9%
Est. Price	~$0.19 @ 500+ (JLCPCB/LCSC)

Supplier Links:

5.5 U.FL Connector (Test / Fallback)¶

Parameter	Value
Type	U.FL or equivalent
Impedance	50 ohm
Est. Price	~$0.15--0.25 USD
BOM Status	DNP in production (test/fallback only)

5.6 3.8V LDO¶

Parameter	Value
Output	3.8V fixed
Max Current	≥2A
Input	5V (from B2B)
Package	SOT-223 or similar (good thermal)
Est. Price	~$0.30--0.60 USD

Part number TBD by CAD designer. Select a 3.8V fixed LDO with ≥2A output, low dropout (<500 mV), and good transient response for 2A burst loads. Consider TPS7A20 series (TI), AP2112K-3.8 (Diodes Inc), or RT9013-38 (Richtek).

5.7 Level Shifter IC¶

Parameter	Value
Channels	6--8 bidirectional
Low side	1.8V (from modem VDD_1V8)
High side	3.3V (from B2B)
Suggested IC	TXB0106 (TI, 6-ch) or TXS0108E (TI, 8-ch)
Est. Price	~$0.20--0.50 USD

5.8 NETLIGHT Development LED¶

Parameter	Value
LED	Green 0402 or 0603
Resistor	1k series (0402), sized for 1.8V drive
Est. Price	~$0.02 total
BOM Status	DNP in production (dev aid only)

5.9 Bulk Capacitors (Modem VBAT)¶

Parameter	Value
Ceramic	2x 22 µF, X5R, 6.3V, 0805 or 1206
Tantalum	1x 100--220 µF, 6.3V, low-ESR
Placement	Close to modem VBAT pins (55--57)

6. PCB Design Notes¶

6.1 Assembly Principle -- Top Side Components Only¶

All components are placed on the top side only of the extension PCB. The bottom side faces the 232204 base PCB across the B2B connector gap (~10--11mm). The B2B socket pins protrude from the bottom side but no other components are placed there.

Layer	Contents
Top	SIM7672E modem, chip antenna, SIM holder, level shifters, LDO, U.FL (DNP), B2B socket body, dev LED, passives
Bottom	B2B socket solder pads only (no components)

The SIM card holder is mounted on the top side with the card insertion slot facing downward -- the SIM card is inserted from underneath the extension board. This provides SIM access from the same side as the USB-C connector on the base PCB.

6.2 Board Dimensions¶

Extension PCB must fit within the enclosure volume above the 232204 base PCB
Board outline constrained by enclosure internal geometry and connector stack-up height
Stack-up: base PCB (~1.6mm) + B2B gap (~10--11mm) + extension PCB (~1.6mm) = ~13--14mm total

6.3 RF Layout¶

Chip antenna placement: At board edge, antenna element extending beyond ground plane edge. No ground pour or copper within 5mm keep-out zone around antenna radiating elements.
Matching network: Pi-network (2--3 pads, 0402) between modem RF pad and antenna feed. Tune with VNA after first prototype.
RF trace: 50 ohm controlled impedance trace from modem RF pad (pin 60) to matching network. Continuous ground plane beneath RF trace, no splits.
U.FL placement: Adjacent to matching network. 0R selector between chip antenna path and U.FL path (only one populated at a time).
Ground plane: The extension board ground plane, connected to the base board via B2B GND pins (pins 2, 3), provides the antenna counterpoise. Maximise ground plane area, especially in the axis perpendicular to the chip antenna.

6.4 Power Layout¶

3.8V LDO close to B2B power input pins -- short, wide input traces from 5V rail
Wide power traces (≥3 mm) for VBAT from LDO output to modem power pins (2A burst current)
Bulk capacitors (≥100 µF total, recommended 300 µF) close to modem VBAT pins
Separate analog and digital ground regions where specified by SIMCom reference design
The modem VDD_1V8 output (pin 15) powers the level shifter low-side supply -- add 100nF decoupling cap close to pin 15

6.5 SIM Routing¶

SIM signals routed locally from modem SIM pins to SIM holder (short traces, same PCB)
No SIM signals cross the B2B connector
ESD protection (TVS diode array) close to SIM holder
Controlled impedance per ISO/IEC 7816 SIM specification

6.6 Level Shifter Placement¶

Place level shifter IC close to B2B connector (on the 3.3V signal path side)
Keep 1.8V traces between modem and level shifter short
VDD_1V8 reference from modem pin 15 to level shifter low-side supply -- add decoupling cap
PWRKEY and RESET use separate NPN/MOSFET circuits (not the TXB0106) due to VBAT voltage domain

6.7 Manufacturing¶

4-layer FR4 (same specification as 230220 -- see PCB Project Brief section 4)
Black solder mask
ENIG surface finish
SMT assembly compatible with same EMS as base PCB
Top-side-only component placement simplifies assembly
On-board chip antenna eliminates manual cable assembly step

7. Test Points¶

TP #	Signal	Expected Value	Notes
TP40	VIN_5V	5.0V	Power from base PCB via B2B
TP41	VBAT_3V8	3.8V	LDO output to modem
TP42	VDD_1V8	1.8V	Modem 1.8V reference (pin 15)
TP43	UART_TX (1.8V side)	Logic	AT command data (modem side, 1.8V)
TP44	UART_RX (1.8V side)	Logic	AT response data (modem side, 1.8V)
TP45	RF_OUT	--	RF signal to antenna / matching network
TP46	SIM_CLK	Logic	SIM clock (local, modem ↔ holder)
TP47	NETLIGHT	Blink pattern	Dev LED should blink when active (1.8V)
TP48	PWRKEY	VBAT domain	Modem power toggle (VBAT level)

LTE Extension Tests¶

8. Revision History¶

Revision	Date	Author	Changes
Rev A	TBD	TBD	Initial design (not in first PCB iteration)

232204 Base Full -- Base PCB this extension connects to
232211 Ext LTE US -- US variant of this extension
ADR #17: LTE Module and Antenna -- Decision rationale
Sales Articles -- Part of subassembly 232504 (EU)
datasheets/A7670_SIM7070_A7672X_Compatible_Design_V1.02.pdf -- SIMCom hardware design reference (pin-compatible family)
datasheets/SIM7672X_Sleep_Mode_Application_Note_V1.00.pdf -- Sleep mode configuration

232210 - EverTag Ext LTE EU¶

1. Overview¶

Key Features¶

2. Block Diagram¶

3. Schematics¶

3.1 LTE Modem -- SIMCom SIM7672E¶

3.2 Board-to-Board Connector (Extension Side -- Socket)¶

B2B Pin Assignment (matches 232204 header)¶

3.3 SIM Card Holder¶

3.4 On-Board Chip Antenna (Primary)¶

3.5 U.FL Test / Fallback Connector¶

3.6 Modem Power Supply (3.8V LDO)¶

3.7 Level Shifters (1.8V ↔ 3.3V)¶

3.8 NETLIGHT Development LED¶

3.9 USB_BOOT Strapping (Pin 6)¶

4. Pin-Out¶

4.1 B2B Connector Signals¶

4.2 Local Signals (Extension Board Only)¶

5. Component Selection¶

5.1 LTE Modem¶

5.2 Board-to-Board Connector (Extension Side -- Socket)¶

5.3 SIM Card Holder¶

5.4 On-Board Chip Antenna¶

5.5 U.FL Connector (Test / Fallback)¶

5.6 3.8V LDO¶

5.7 Level Shifter IC¶

5.8 NETLIGHT Development LED¶

5.9 Bulk Capacitors (Modem VBAT)¶

6. PCB Design Notes¶

6.1 Assembly Principle -- Top Side Components Only¶

6.2 Board Dimensions¶

6.3 RF Layout¶

6.4 Power Layout¶

6.5 SIM Routing¶

6.6 Level Shifter Placement¶

6.7 Manufacturing¶

7. Test Points¶

LTE Extension Tests¶

8. Revision History¶

Related Documents¶