LZ2x1 Series Hardware Design Guidelines

These guidelines are intended to serve as the reference when you develop with LZ2x1 series modules. It helps you get an overall understanding of the product specifications and assists in developing IoT products and applications.

This topic describes the hardware design guidelines in terms of features, specifications, reliability tests, test standards, development process, radio frequency (RF) metrics, and circuit designs.

Background

Glossary

Abbreviation	Spelled-out
ESD	Electrostatic discharge
USB	Universal serial bus
UART	Universal asynchronous receiver-transmitter
SIM	Subscriber identification module
SPI	Serial peripheral interface
I2C	Inter-integrated circuit
I/O	Input/Output
GPIO	General-purpose input/output
TBD	To be determined
RTC	Real time clock
ADC	Analog-to-digital converter

References

These guidelines apply to LZ2x1 series modules, including LZ201-CN, LZ211-CN, LZ201-EAU, and LZ211-EAU.

• LZ201-CN Datasheet
• LZ211-CN Datasheet
• LZ211-EAU Datasheet
• LZ2x1 Series Hardware Design Guidelines (This documentation)
• LZ2x1 Series Schematic Diagram
• LZ2x1 Series Open CPU GPIO Configuration
• LTE Cat.1 Serial Protocol

Product overview

The LZ2x1 series is a family of LTE Cat.1 cellular modules from Tuya Smart. The LZ2x1 module consists of a highly integrated LTE Cat.1 chip UIS8910DM and peripheral circuits. It has a built-in LTE Cat.1 network communication protocol stack and library functions.

The LZ2x1 module is built around an Arm Cortex-A5 processor and Cat.1 bis modem and embedded with 64 MB NOR flash and 128 MB PSRAM. It provides a wide array of interfaces including USB, UART, SDIO, SPI, I2C, I2S, and ADC for supporting peripherals such as the display, camera, keyboard matrix circuit, microphone, speaker, charger, microSD card, and USIM card.

Models

Frequency bands	LZ201-CN	LZ211-CN	LZ201-EAU	LZ211-EAU
LTE FDD	Band 1, 3, 5, 8	Band 1, 3, 5, 8	Band 1, 3, 5, 7, 8, 20, 28A	Band 1, 3, 5, 7, 8, 20, 28A
LTE TDD	Band 34, 38, 39, 40, 41	Band 34, 38, 39, 40, 41	Band 38, 40, 41	Band 38, 40, 41
GSM	Not supported	Not supported	900/1800	900/1800
GNSS	Not supported	Support	Not supported	Support
Bluetooth Low Energy 4.2	Support	Support	Not supported	Not supported
Wi-Fi Scan	Support	Support	Not supported	Support

Features

Feature	Description
Processor	Arm Cortex-A5 500 MHz microprocessor
Voltage	Operating voltage: 3.4V to 4.3V Typical operating voltage: 3.8V
SIM card	1.8V or 3V supported
LTE-FDD Cat.1 speed	Maximum download speed of 10 Mbps Maximum upload speed of 5 Mbps
LTE-TDD Cat.1 speed	Maximum download speed of 8.2 Mbps Maximum upload speed of 3.4 Mbps
GSM speed	Multislot Class 12 Download speed of 85.6 kbps Upload speed of 85.6 kbps
Bluetooth	Bluetooth Low Energy 4.2. Pairing over Bluetooth is not stable currently. It is recommended to set pairing with QR code as the preferred mode.
Wi-Fi	Only Wi-Fi scan is supported, used for indoor positioning.
Antenna interface	LTE, Bluetooth Low Energy, and Wi-Fi antennas as well as GNSS antennas
Port	1 USB 2.0 port, 3 UART ports, 2 I2C ports, 1 PCM/I2C port, 1 SDIO port, 1 SPI port, and 3 ADC ports
Display	SPI display in 320 × 240 pixel resolution at 30 fps
Camera	SPI/MIPI camera in 640 × 480 pixel resolution
Audio	1-channel microphone and 1-channel speaker
MicroSD card	Support
Operating temperature	Operation temperature range: -30°C to +75°C 1 Extended temperature range: -40°C to +85°C 2
Software updates	USB update or OTA update

Appearance

Pin configuration and functions

LZ2x1 is equipped with a total of 144 pins, including 80 LCC pins and 64 LGA pins.

The pinout is as follows:

I/O parameters definition

Type	Description
P	Power supply
I	Input
O	Output
IO	Input/Output

Pin description

Pin No.	Pin name	I/O type	Description
1	WAKEUP_IN	I	External circuit wakes up the module. It can be used as GPIO10 in OpenCPU mode. If it is unused, keep it open.
2	AP_READY*	I	Used to inform the module whether the application processor is in sleep mode. It can be used as GPIO11 in OpenCPU mode. If it is unused, keep it open.
3	WAKEUP_OUT*	O	The module wakes up the external circuit. It can be used as GPIO5 in OpenCPU mode. If it is unused, keep it open.
4	W_DISABLE_N*	I	Used to force the module into airplane mode. It can be used as GPIO8 in OpenCPU mode. If it is unused, keep it open.
5	NET_MODE	PI	Indicate the module’s network registration mode, which applies when the module operates in self-processing mode. NET_MODE is a current source and connected to the LED GND pin.
6	NET_STATUS*	O	Indicate the module network activity status. It can be used as GPIO9 in OpenCPU mode.
7	VDD_EXT	PO	1.8V voltage output. It can provide pull-up for the external circuit. If it is unused, keep it open.
8	GND	-	The ground pin.
9	GND	-	The ground pin.
10	USIM_GND	-	The ground pin. It shares the same network as GND.
11	ISENSE	I	Measure the charge current.
12	VBAT_SENSE	I	Measure battery voltage. Connect it close to the positive terminal of batteries to sense the battery voltage. If the battery is not used, disable low voltage shutdown in the software. Otherwise, the module will shut down on low voltage.
13	USIM_DET	I	USIM card hot-plug detection, which is disabled by default in the software. Pull this pin up to VDD_EXT.
14	USIM_VDD	PO	Power supply for the USIM card. Either 1.8V or 3.0V is supported by the module automatically.
15	USIM_DATA	IO	Data signal of USIM card.
16	USIM_CLK	O	USIM card clock signal.
17	USIM_RST	O	Reset signal of the USIM card.
18	VDRV	O	Enable the charger circuit.
19	GND	-	The ground pin.
20	RESET_N	I	Reset the module. Active low.
21	PWRKEY	I	Power on or off the system.
22	GND	-	The ground pin.
23	SD_INS_DET	I	SD card insertion detection. It can be used as GPIO7 in OpenCPU mode.
24	PCM_DIN	I	PCM data input. It can be used as GPIO2 in OpenCPU mode.
25	PCM_DOUT	O	PCM data output. It can be used as GPIO3 in OpenCPU mode.
26	PCM_SYNC	IO	PCM data sync. It can be used as GPIO1 in OpenCPU mode.
27	PCM_CLK	IO	PCM audio clock signal. It can be used as GPIO0 in OpenCPU mode.
28	SD_DATA3	I	SD card SDIO data bit 3. It can be used as WLAN SDIO.
29	SD_DATA2	I	SD card SDIO data bit 2. It can be used as WLAN SDIO.
30	SD_DATA1	I	SD card SDIO data bit 1. It can be used as WLAN SDIO.
31	SD_DATA0	I	SD card SDIO data bit 0. It can be used as WLAN SDIO.
32	SD_CLK	O	SD card SDIO clock signal. It can be used as WLAN SDIO.
33	SD_CMD	IO	SD card SDIO command signal. It can be used as WLAN SDIO.
34	VDD_SDIO	PO	Power supply for SD card. It can be used as WLAN SDIO.
35	ANT_BT/WIFI	AIO	Bluetooth and Wi-Fi antenna.
36	GND	-	The ground pin.
37	SPI_CS_N	I	SPI chip select
38	SPI_MOSI	I	SPI MOSI
39	SPI_MISO	O	SPI MISO
40	SPI_CLK	O	SPI clock signal
41	I2C_SCL	OD	I2C clock signal. It can be used as GPIO14 in OpenCPU mode.
42	I2C_SDA	OD	I2C data signal. It can be used as GPIO15 in OpenCPU mode.
43	ADC2	AI	Analog to digital converter interface 2.
44	ADC1	AI	Analog to digital converter interface 1.
45	ADC0	AI	Analog to digital converter interface 0.
46	GND	-	The ground pin.
47	ANT_GNSS	AI	GNSS antenna, supported by LZ211 series and not supported by LZ201 series.
48	GND	-	The ground pin.
49	ANT_MAIN	AIO	Main antenna interface.
50 to 54	GND	-	The ground pin.
55	RESERVED	-	Reserved
56	GND	-	The ground pin.
57	VBAT_RF	P	Power supply for module RF part. Supply voltage: 3.4V to 4.3V. Nominal voltage: 3.8V. Peak current: 2A.
58	VBAT_RF	P	Power supply for module RF part. Supply voltage: 3.4V to 4.3V. Nominal voltage: 3.8V. Peak current: 2A.
59	VBAT_BB	P	Power supply for baseband part. Supply voltage: 3.4V to 4.3V. Nominal voltage: 3.8V. Current: 1A.
60	VBAT_BB	P	Power supply for baseband part. Supply voltage: 3.4V to 4.3V. Nominal voltage: 3.8V. Current: 1A.
61	STATUS*	O	Module status output.
62	UART1_RI*	O	Ring indicator. It can be used as GPIO12 in OpenCPU mode.
63	RESERVED63	O	Reserved
64	UART1_CTS	O	UART 1 clear to send. It can be used as GPIO18 in OpenCPU mode.
65	UART1_RTS	I	UART 1 request to send. It can be used as GPIO19 in OpenCPU mode.
66	UART1_DTR*	I	Wake up the module.
67	UART1_TXD	O	UART 1 transmit data. It can be connected to an external MCU.
68	UART1_RXD	I	UART 1 receive data. It can be connected to an external MCU.
69	USB_DP	IO	USB high-speed differential transceiver (positive). It can be used to download code to the module.
70	USB_DM	IO	USB high-speed differential transceiver (negative). It can be used to download code to the module.
71	USB_VBUS	PI	Detect USB insertion.
72	GND	-	The ground pin.
73	SPK_P	O	Speaker output signal (positive).
74	SPK_N	O	Speaker output signal (negative).
75	MIC_P	I	Microphone input signal (positive).
76	GND	-	The ground pin.
77	MIC_N	I	Microphone input signal (negative).
78	KEYIN1	IO	Key input 1.
79	KEYIN2	IO	Key input 2.
80	KEYIN3	IO	Key input 3.
81	KEYIN4	IO	Key input 4.
82	KEYIN5	IO	Key input 5.
83	KEYOUT0	IO	Key output 0.
84	KEYOUT1	IO	Key output 1.
85 to 112	GND	-	The ground pin.
113	KEYOUT2	IO	Key output 2.
114	KEYOUT3	IO	Key output 3.
115	USBBOOT	IO	Key input 0. Pulling up this pin to VDD_EXT before power-on will make the module enter USB download mode. Leaving this pin floating will boot the module in normal mode.
116	RESERVED116	-	Reserved. Keep it open.
117	CLK26M_OUT*	O	26M clock signal.
118	RESERVED118	-	Reserved. Keep it open.
119	LCD_FMARK	O	SPI LCD frame sync signal
120	LCD_RSTB	O	SPI LCD reset signal
121	LCD_SEL	O	SPI LCD selection
122	LCD_CS	O	SPI LCD chip select
123	LCD_CLK	O	SPI LCD clock signal
124	LCD_SDC	O	SPI LCD data command selection
125	LCD_SIO	O	SPI LCD data signal
126	VDDLCD	P	External LCD power supply
127	PM_ENABLE	O	External power LDO control. It can be used as GPIO13 in OpenCPU mode.
128	VDDCAMA	P	Power supply for camera VCAMA
129	CAM_PWDN	IO	Camera CAM_PWDN signal
130	CAM_SI1	IO	Camera CAM_SI1 signal
131	CAM_SI0	IO	Camera CAM_SI0 signal
132	CAM_RSTL	IO	Camera CAM_RSTL signal
133	CAM_REFCLK	O	Camera CAM_REFCLK signal
134	CAM_SCK	IO	Camera CAM_SCK signal
135	UART2_RXD/WAKE_WLAN	O	UART 2 receive data. It can be used for the external Wi-Fi module to wake up the LZ201* module or used as GPIO20 in OpenCPU mode. Downloading code to the module is supported.
136	UART2_TXD/WLAN_EN	O	UART 2 transmit data. It can be used to enable the external Wi-Fi module* or used as GPIO21 in OpenCPU mode. Downloading code to the module is supported.
137	UART3_RXD/KEYOUT4	I	UART 3 receive data. It can be used as KEYOUT4.
138	UART3_TXD/KEYOUT5	O	UART 3 transmit data. It can be used as KEYOUT5.
139	ZSP_UART_TXD/BT_EN	O	ZSP log output. It can be used to enable the external Bluetooth Low Energy mesh module* or used as GPIO22 in OpenCPU mode.
140	VDDCAMD	P	Power supply for camera VCAMD
141	I2C2_SCL	IO	I2C clock signal.
142	I2C2_SDA	IO	I2C data signal. It can be used as GPIO17 in OpenCPU mode.
143	DBG_RXD	I	Debugging interface, used for the module to receive data.
144	DBG_TXD	O	Debugging interface, used for the module to transmit data.

Power supply

Power and ground pins

LZ2X1 can be powered by a battery or an external power supply. The ground pin and signal ground pin must be connected to the ground plane on the PCB. Otherwise, the overall performance of the module might be affected.

Pin No.	Signal	Description	Min	Typical	Max	Unit
59 and 60	VBAT_BB	Power supply for the baseband part.	3.4	3.8	4.3	V
57 and 58	VBAT_PA	Power supply for the RF part.	3.4	3.8	4.3	V
8, 9, 10, 19, 22, 36, 46, 48, 50-54, 56, 72, 76, 85-112	GND	GND	-	-	-	-

Power supply requirements

• The supply voltage of the LZ2X1 module ranges from 3.4V to 4.3V, with a peak current of 2A.

  • If the difference between the input and output voltage is small, you can use a low-dropout (LDO) regulator to maintain the required system voltage.
  • If the difference between the input and output voltage is large, you can use a DC-to-DC converter to regulate the output voltage.

• Voltage drop: When the module is working, make sure its input voltage will never drop below 3.4V and the ripple voltage is less than 300 mV.

  

• Voltage regulator and filter capacitor:

  • Capacitors used for the voltage regulation circuit of a power supply: 100 μF × 2, 10 μF
  • Filter capacitors on digital signals: 1 μF, 0.1 μF
  • Filter capacitors on high-frequency signals: 33 pF, 10 pF

• Electrostatic discharge protection: Add a TVS diode on the VBAT trace (near VBAT pins) to improve surge voltage withstand capability.

• In principle, star routing topology is required. The longer the VBAT trace is, the wider it should be.

• If the module is powered by a battery, you can enable low voltage (less than 3.38V) shutdown, with consideration of the power of other components on the backplane. Otherwise, the module might not be powered on due to battery over-discharge.

A reference circuit for the power supply is illustrated in the following figure.

Power on/reset

Pin description

Pin No.	Signal	Description
21	PWRKEY	Power on the module.
20	RESET_N	Reset the module.

Applications

• Power on: The module will be powered on after the PWRKEY pin is driven to a low level for at least 1.5 seconds and then pulled up or left floating.

  

• Auto power-on: If you want the module to be powered on whenever a power source is connected and do not need the shutdown feature, you can pull down PWRKEY to ground.

• Reset: The module will be reset after the RESET pin is driven to a low level for at least 35 ms and then pulled up or left floating.

  

• An open drain/collector driver is recommended, as shown in the following schematics.

  • Power-on circuit
  
  • Reset circuit
  

UART interface

Pin description

The module provides three UART interfaces:

• UART 1: used to connect to your MCU. The serial data transmission follows Tuya’s protocol. The baud rate is 115200 bps by default.

• UART 2: used to connect to peripheral devices. For modules with the GNSS feature, this interface has been occupied by the internal GNSS chip.

• UART 3: used to connect to peripheral devices.

  Pin No.	Signal	Description
  68	UART1_RXD	UART 1 receive data.
  67	UART1_TXD	UART 1 transmit data.
  64	UART1_CTS	UART 1 clear to send.
  65	UART1_RTS	UART 1 request to send.
  135	UART2_RXD	UART 2 receive data.
  136	UART2_TXD	UART 2 transmit data.
  137	UART3_RXD	UART 3 receive data.
  138	UART3_TXD	UART 3 transmit data.

Applications

The module provides 1.8V UART interfaces. A level translator should be used if the application is equipped with a 3.3V or 5V UART interface. As shown in the following figure:

Alternatively, use a triode to translate voltage levels.

USB interface

Pin description

The USB interface conforms to USB 2.0 specifications and can be used to download code to the module.

Pin No.	Signal	Description
69	USB_DP	USB high-speed differential transceiver (positive). It can be used to download code to the module.
70	USB_DM	USB high-speed differential transceiver (negative). It can be used to download code to the module.
71	USB_VBUS	Data signal of USIM card.
115	USBBOOT	Pulling up this pin to VDD_EXT before power-on will make the module enter USB download mode. Leaving this pin floating will boot the module in normal mode.

Applications

• MCU solutions

  

• Micro-USB cable

  

Circuit design

• Pull up USBBOOT to VDD_EXT to boot the module in USB download mode.

• Make sure to route the USB signal traces as differential pairs with total grounding. The impedance of USB differential trace is 90Ω.

• Do not route signal traces under the power supply, RF signal traces, and other sensitive signal traces. It is important to route the USB differential traces in the inner layer with ground shielding on not only the upper and lower layers but also the right and left sides.

• Connect a common mode choke between the MCU and module in series to improve EMI suppression.

• VBUS is used to detect the presence of the USB bus. If the USB port on your MCU does not support the suspend mode, you can disconnect VBUS to make the module enter sleep mode.

  

• Considering connection to micro-USB devices, place the TVS diode as close to the USB port as possible with a parasitic capacitance of less than 2 pF.

SIM card interface

Pin description

Pin No.	Signal	Description
13	USIM_DET	USIM card hot-plug detection, which is disabled by default in the software. Pull this pin up to VDD_EXT.
14	USIM_VDD	Power supply for USIM card. Either 1.8V or 3.0V is supported by the module automatically.
15	USIM_DATA	Data signal of USIM card.
16	USIM_CLK	USIM card clock signal.
17	USIM_RST	Reset signal of the USIM card.

Applications

Circuit design

• Place the SIM card connector near the module. Keep the trace length as less than 200 mm as possible.
• Place a 2.2 μF decouple capacitor between USIM_VDD and GND, close to the SIM card connector.
• Place a 10 to 20K pull-up resistor on the USIM_DATA to reduce EMI.
• Place the RF bypass capacitors (33 pF) close to the SIM card connector on all signal traces (USIM_DATA, USIM_RST, and USIM_CLK) to improve EMI suppression.
• Keep USIM card signals away from RF and VBAT traces. To avoid crosstalk between SIM_DATA and SIM_CLK, keep them away from each other.
• In order to offer good ESD protection, it is recommended to add a TVS diode array with a parasitic capacitance of less than 15 pF. The ESD protection device should be placed as close to the SIM card connector as possible, and make sure the SIM card signal lines go through the ESD protection device first and then to the module.
• For the design of SIM card hot-swapping, the USIM_DET is shorted to the ground when no card is inserted. When a card is inserted, USIM_DET floats and is pulled up by VDD_EXT. If you do not use USIM_DET, pull it up to VDD_EXT.

SD card interface

Pin description

The memory card interface provides access to memory cards compliant with SD 2.0 and SDIO 1.1 standards.

Pin No.	Signal	Description
28	SD_DATA3	SD card SDIO data bit 3.
29	SD_DATA2	SD card SDIO data bit 2.
30	SD_DATA1	SD card SDIO data bit 1.
31	SD_DATA0	SD card SDIO data bit 0.
32	SD_CLK	SD card SDIO clock signal.
33	SD_CMD	SD card SDIO command signal.
34	VDD_SDIO	SD card SDIO bus pull-up power.

Applications

Circuit design

• The maximum output current of VDD_SDIO is 150 mA. If the SD card current consumption exceeds 150 mA, an external power supply is needed.
• Connect a 22Ω resistor between the SD_CLK and SD signal trace in series to reduce EMI.
• Reserve a pad for 0201 33 pF capacitor on the signal trace.
• Reserve a pad for a pull-up resistor (100 kΩ is recommended) on the SD signal trace for increasing the stability of the bus line. VDD_SDIO is the pull-up power supply.
• SD_CLK needs ground shielding. Surround SD signal traces with total grounding to prevent any possible crosstalk and noise coupling from other signal sources.
• It is recommended to keep the same trace length for SD_CLK, SD_DATA[0:3], and SD_CMD, with a length difference of less than 1 mm. The total length should not exceed 50 mm.
• In order to offer good ESD protection, it is recommended to add a TVS diode array with a parasitic capacitance of less than 15 pF. The ESD protection device should be placed as close to the SIM card connector as possible, and make sure the SIM card signal lines go through the ESD protection device first and then to the module.

Network status indication

Pin description

Pin No.	Signal	Description
5	NET_MODE	Indicate the module’s network registration mode, which applies when the module operates in self-processing mode. NET_MODE is a current source and connected to the LED GND pin.

Applications

• Status indication is disabled by default. The module reports the network status to the MCU through the serial port. To turn on status indication, you need to enable self-processing mode in the software.
• NET_MODE is the current source so it should be connected to the negative terminal of the LED.

SPI interface

Pin description

Pin No.	Signal	Description
37	SPI_CS_N	SPI chip select
38	SPI_MOSI	Controller out and agent in
39	SPI_MISO	Controller in and agent out
40	SPI_ SCLK	SPI serial clock signal

Applications

The module provides 1.8V SPI interface. A level translator should be used if the application is equipped with a 3.3V UART interface.

A reference circuit is illustrated in the following figure.

I2C bus

Pin description

Pin No.	Signal	Description
41	I2C_SCL	I2C serial clock line
42	I2C_SDA	I2C serial data line

I2C is a simple serial communication bus protocol that uses just two bus wires, a serial data wire (SDA) and a serial clock wire (SCL). I2C is integrated into many ICs and allows devices to communicate directly with each other. Each device is recognized by a unique address to differentiate from other devices on the same I2C bus and can operate either as a transmitter or a receiver depending on its function.

Applications

The I2C bus must be pulled up to VDD_EXT.

PCM interface

Pin description

Pin No.	Signal	Description
24	PCM_DIN	PCM audio input
25	PCM_DOUT	PCM audio output
26	PCM_SYNC	PCM audio sync
27	PCM_CLK	PCM audio clock signal

Applications

The PCM and I2C are 1.8V. If the codec chip is 3.3V, a level converter is required.

SPI flash interface

The module has a built-in 64 MB NOR flash. If it is not sufficient for your applications, you can add an external SPI flash. This interface can be reused as SPI LCD.

Pin description

Pin No.	Signal	Description
119	LCD_FRAMK	Reuse SPI flash 1 serial data3
121	LCD_SEL	Reuse SPI flash 1 serial data2
122	LCD_CS	Reuse SPI flash 1 serial data1
123	LCD_CLK	Reuse SPI flash 1 serial data0
124	LCD_SDC	Reuse SPI flash 1 CS
125	LCD_SIO	Reuse SPI flash 1 clock

Applications

Charger interface

Pin No.	Signal	Description
11	ISENSE	Measure the charge current.
12	VBAT_SENSE	Measure battery voltage. Connect it close to the positive terminal of batteries to sense the battery voltage. If the battery is not used, disable low voltage shutdown in the software. Otherwise, the module will shut down on low voltage.
18	VDRV	Enable the charger circuit.
71	USB_VBUS	Detect charging voltage input.

Applications

• Linear charger circuit diagram:

  

• Discrete component circuit diagram:

  

Circuit design

• Considering the thermal design, you can use a linear charger if the charge current is less than 0.7A. Otherwise, switching chargers are recommended.
• To get an accurate charging current, ISENSE and VBAT_SENSE can be routed as a pseudo-differential mode (0.075 mm/0.075 mm/0.075 mm). Route the differential traces with ground shielding on the right and left sides.
• Place the shunt resistor (0.068Ω±1%, 0.125W, 0805) close to the PNP triode. The trace width of the charger should not be less than 1 mm. The 4-Pin Land Pattern Design from UNISOC is recommended.
• The copper pour for the anode (collector) of the PNP triode should not be less than 30 mm². It is recommended to connect the adjacent layers to the ground for better heat dissipation.
• You can add an NTC thermistor within 1.5 mm around the PNP component to control temperature.

GPIO interface

Some pins can be used as GPIOs if the module uses open CPU SDK-based firmware.

For more information, see LZ2x1 Series Open CPU GPIO Configuration.

Antenna

Pin description

Pin No.	Signal	Description
35	ANT_BT/WIFI	Bluetooth Low Energy or Wi-Fi antenna
47	ANT_GNSS	GNSS antenna, supported by LZ211 and not supported by LZ201.
49	ANT_MAIN	LTE antenna

Antenna matching circuit

In order to achieve better RF performance, it is recommended to place the π-type matching components as close to the antenna as possible.

By default, the capacitors (C1/C2) are not mounted and a 0Ω resistor is mounted on L1.

• LTE, Bluetooth Low Energy, and Wi-Fi antennas as well as GNSS passive antennas

  

• GNSS passive/active antennas

  Select a passive or active antenna as needed. If you use an active antenna, choose an appropriate feeding voltage based on the antenna datasheet.

  

RF layout

For MCU PCB, the characteristic impedance of all RF traces should be controlled as 50Ω. A microstrip line is used for impedance control.

Microstrip line design on PCB

Principles in RF layout design:

• The distance between the RF pins and the RF connector should be as short as possible. All the right angle traces should be changed to 135° or curved ones.
• The reference ground of RF traces should be complete. Add some ground vias around RF traces. The distance between the ground vias and RF traces should be no less than two times the width of RF signal traces.
• The GND pins are adjacent to RF pins and should be fully connected to the ground.
• There should be a distance between the pad connected to the signal pin and the ground plane.
• Use impedance simulation tool to control the characteristic impedance of RF traces as 50Ω.
• If you use an external antenna, add a TVS diode to prevent ESD damage. The TVS diode’s junction capacitance (Cj in pF) should be less than 0.5 pF.

The following figure provides parameters used for impedance control. You can adjust the trace width properly to get the trace impedance closer to 50Ω.

Antenna design requirements

• The antenna should be kept away from components that are more likely to generate EMI, such as power source and data line.
• To maximize the RF performance, the distance between the antenna and the PCB or mental materials should be at least 15 mm.
• Make sure that the enclosure surrounding the antenna is not metal materials. Otherwise, the radiation performance might be degraded. It is recommended to hollow out the breakout board around the antenna area.

Antenna types

This module does not come with an antenna, so an external antenna is required. You can choose one from the external rubber antenna, helical antenna, FPC antenna with IPEX connector, and PCB antenna. The antenna type can be monopole, planar inverted-F antenna (PIFA), inverted-F antenna (IFA), loop, and more.

The following figure shows the common antennas.

• Rubber antenna

  

• FPC antenna with IPEX connector

  

• Built-in FPC antenna

  

• GPS antenna

  Adopt an active antenna by adding an external power source.

  

• Ceramic GPS antenna

  

• PCB antennas for Bluetooth

  

Reliability design

EMC and ESD suppression design guide

Electromagnetic compatibility (EMC) is one of the essential considerations in designing for signal integrity and power integrity.

• When you design the peripheral circuit, have two times the width of the trace when routing signals close to each other to minimize noise coupling and generation.
• Place decoupling capacitors close to voltage pins. Keep the high-frequency and high-speed circuits and sensitive circuits away from the edge of the PCB. To reduce crosstalk between signals, increase the spacing between the traces. Provide shielding for components that emit RFI and EMI waves to protect sensitive signals from interference.

Design considerations for ESD circuit protection.

• Place ESD protection devices close to the critical signal I/Os, such as the SIM card, USB port, and TF card.
• In PCB layout and design, make sure the metal shielding enclosure is fully connected to the ground.

PCB pad design

It is recommended to design the 64 pads placed in the middle of the PCB as per the dimensions specified in the structure diagram. Extend the 80 pads around the PCB to the module for over 0.3 mm and the other three sides of the pads for 0.05 mm.

Thermal design

The module generates heat when it works or might be affected by high-temperature components. The module design ensures good heat dissipation. When connecting the module to the PCB, connect the thermal pad to the ground properly to ensure thermal conduction and balance and better electrical performance.

Packing and manufacturing

Mechanical dimensions

The dimensions are 29 mm±0.35 (W) × 32 mm±0.35 (L) × 2.4 mm±0.15 (H), as shown below. The PCB thickness is 0.8 mm ±0.1 mm.

SMT package

Stencil opening design

• Stencil thickness: The stencil thickness of the area for the module should be partly stepped up to 0.18 mm–0.2 mm.
• LCC pins: The stencil openings are shrunk inward by 0.1 mm, and moved outward by 1 mm along the direction of length. Along the width direction, the stencil openings are shrunk inward by 0.16 mm (each side by 0.08 mm) with a length of 1.4 mm (module’s lead length, avoiding solder beads), and are moved outward by 0.2 mm (each side by 0.1 mm) with a length of 2 mm (exposed on the areas outside of the bottom of the module leads to increase tinning).
• LGA pins: The total opening area of the stencil should be 60% of the total. If it exceeds 60%, you can set a pitch of 0.3 mm.