Introduction to NB Module - NM1

About This Document

Applicable Scope

This document describes hardware interface specifications, electrical features, mechanical specifications, and other related in formation about the NM1 module to help you design and develop NM1 module hardware.

Purpose

This document provides NM1 module design and development bases. Through this document, you can know the NM1 module and its technical parameters and develop related functional product or devices. In addition to functional features and technical parameters, this document also describes the product reliability test, related test standards, service function implementation process, RF performance indicators, and circuit design.

Acronyms and Abbreviations

Table 1-2 Acronyms and abbreviations

Acronyms

Full Spelling

ESD

electrostatic discharge

USB

Universal Serial Bus

UART

universal asynchronous receiver/transmitter

SIM

subscriber identity module

SPI

serial peripheral interface

I2C

inter-integrated circuit

I/O

Input/Output

GPIO

General Purpose Input/Output

TDB

To be determined

RTC

real-time clock

ADC

analog to digital converter

Product Overview

NM1 is a compact , high performance, and low power NB IoT series module. It has the following features:

Supports the B1,B3, B5, B8, B20 frequency bands (B2/B23/B13/B17/B18/B19/B25/B26/B28/B66 are in developing stage).
Provides the SIM card interface (1.8 V), USB 1.1 interface, UART interface, SPI, I 2 C interface, and GPIO interface.

Package Dimensions

The NM1 module has 66 pins. Its dimensions is 17.7 2.4 mm (H) x 17.7 mm (W) x 15.8 mm (D).

Technical Parameters

Table 2-1 describes mechanical features, baseband features, RF features, technical standards, and environment features of the NM1 module.

Table 2-1 Technical parameters of the NM1 module

Item

Parameter

Specifications

Mechanical features

Package size and type

17.7 mm x 15.8 mm x 2.6 mm Stamp hole (52 pins) and base pad (14 pins)

Module

Platform

MT2625

Module

Processor architecture

ARM Cortex-M4

Module

SIM card interface

1.8 V

Module

USB interface

USB 1.1

Module

Voltage

2.1 V to 3.63 V

Module

Working mode

Active: The NM1 module is active and can send and receive data. All functions are available. An active NM1 module can switch to the idle or PSM mode. Idle: The NM1 module is in idle state, connected to a network, and can receive paging messages. An idle NM1 module can switch to the active or PSM mode. PSM: Only RTC of the module works, and the module is disconnected from the network and cannot receive paging messages. The NM1 module is woken up from the PSM mode when the timer expires or the PWRKEY and PSM_EINT* pins are lowered.

Module

Power-saving

In PSM mode, the NM1 module consumes the minimum power of 5 µA. The PSM mode is provided to reduce power consumption and prolong the power supply duration of the battery.

Module

Serial port

Primary serial interface: transmits AT commands and data. The default baud rate is 115.2 kbit/s. It can also be used for firmware upgrade and the baud rate is 921.6 kbit/s. Debugging serial interface: exports log information for software commissioning. Auxiliary serial interface: transmits AT commands and data.

Module

Working current

TBD

Module

RTC

Supported

Module

ADC*

The NM1 module has a 10-bit analog-digit conversion input interface to measure the voltage. This interface works in both active and idle modes.

Module

RI signal*

When the NM1 module receives SMS messages or exports URC, it notifies the DTE over the RI pin.

Module

Network status indication*

The NETLIGHT signal indicates the module's network connection status.

Frequency band

B1, B2*, B3, B5, B8, B12*, B13*, B17*, B18*, B19*, B20, B25*, B26*, B28*, and B66*

Maximum TX power

23±2 dBm

Receiving sensitivity

TBD

Main antenna interface

Supported

Antenna interface

Characteristic impedance of 50 ohms. The antenna is provided by a third party, but not Tuya.

Technical standard

Data rate

Single-tone: downlink 25.5 kbit/s and uplink 16.7 kbit/s Multi-tone*: downlink 25.5 kbit/s and uplink 62.5 kbit/s

Technical standard

Network protocol

UDP/TCP/CoAP/LWM2M/PPP*/SSL*/DTLS*/FTP*/HTTP*/MQTT*/HTTPS*

Environment feature

Temperature

Normal operating temperature: –35°C to +75°C1 Extended operating temperature: –40°C to +85°C2 Storage temperature: –40°C to +90°C

application

SMS*

Text and packet data unit (PDU) modes

application

Upgrade

Upgrade is performed over the primary serial interface.

Note:

1) When the NM1 module works at a temperature within the normal operating temperature range 1 , its performance complies with 3GPP standards.

2) When the NM1 module works at a temperature within the extended operating temperature range 2 , it works properly, has the SMS* and data transmission functions, and will not have unrecoverable faults. The RF spectrum and network are not affected. Several indicators, for example, the output power, may exceed the 3GPP limits. After the operating temperature is restored to the normal operating temperature, all NM1 module indicators can meet 3GPP standard requirements.

3) A feature with an asterisk (*) is being developed.

Product Functions

Baseband Functions

The NM1 module baseband includes the USB interface signal, SIM card interface signal, I 2 C interface signal, UART interface signal, working status indicator signal, module startup and reset signals, and multiplexing control signals, power supply, and grounding of multiple GPIO interfaces.

RF Functions

Table 2-2 Working frequency bands

Working Frequency Band

Uplink (MHz)

Downlink (MHz)

1920–1980

2110–2170

B2*

1850–1910

1930–1990

1710–1785

1805–1880

824–849

869–894

880–915

925–960

B12*

699–716

729–746

B13*

777–787

746–756

B17*

704–716

734–746

B18*

815–830

860–875

B19*

830–845

875–890

B20

832–862

791–821

B25*

1850–1915

1930–1995

B26*

814–849

859–894

B28*

703–748

758–803

B66*

1710–1780

2110–2200

Note: The NM1 module is being developed to support the frequency bands with an asterisk (*).

Table2-3 Line loss requirements

Frequency Band

Requirement

LTE B5, B8, B12*, B13*, B17*, B18*, B19* , B20, B26* , and B28*

Line loss < 1 dB

LTE B1, B2*, B3, B25*, and B66*

Line loss < 1.5 dB

Table 2-4 Antenna requirements

Item

Requirement

Frequency band

LTE B1, B2*, B3, B5, B8, B12*, B13*, B17*, B18*, B19*, B20, B25*, B26*, B28*, and B66*

Standing wave ratio (SWR)

≤ 2

Efficiency (%)

≥ 30

Maximum input power (W)

Input impedance (ohm)

Polarization type

Linear polarization

Note: The NM1 module is being developed to support the frequency bands with an asterisk (*).

Table 2-5 Conducted RF transmit power

Frequency Band

Maximum Value (dBm)

Minimum Value (dBm)

23±2 dBm

< –39

B2*

23±2 dBm

< –39

23±2 dBm

< –39

23±2 dBm

< –39

23±2 dBm

< –39

B12*

23±2 dBm

< –39

B13*

23±2 dBm

< –39

B17*

23±2 dBm

< –39

B18*

23±2 dBm

< –39

B19*

23±2 dBm

< –39

B20

23±2 dBm

< –39

B25*

23±2 dBm

< –39

B26*

23±2 dBm

< –39

B28*

23±2 dBm

< –39

B66*

23±2 dBm

< –39

Note:

1) The designed conducted RF transmit power complies with the NB IoT protocol in 3GPP Release 13 and Release 14.

2) The NM1 module is being developed to support the frequency bands with an asterisk (*).

Interfaces

Pin Definition

Pin Symbols

Table 3-1 Pin symbols

Pin Symbol

Description

Input

Output

I/O

Input/Output

Pin Configuration Diagram

Figure 3-1 shows the NM1 module's interface pins.

Pins

Table 3-2 Interface pin definition

Pin No.

Analog Signal Definition

Pin Attribute

Input/Output

Pin Voltage (V)

Remarks

AGND

GND

N/A

GPIO0

N/A

1.8

N/A

SPI_MISO

Primary device input and secondary device output signal

1.8

N/A

SPI_MOSI

Primary device output and secondary device input signal

1.8

N/A

SPI_SCLK

Serial clock signal

1.8

N/A

SPI_CS

Chip selection signal

1.8

N/A

PWRKEY

Lower PWRKEY to power on the NM1 module.

Maximum value of VIL: 0.3 x VBAT Minimum value of VIH: 0.7 x VBAT

N/A

GPIO22

N/A

ADC0

Common analog-digit conversion interface

0–1.4 V

N/A

SIM_GND

GND dedicated for the SIM card

N/A

SIM_DATA

SIM card data signal

I/O

Maximum value of VIL: 0.25 x SIM_VDD Minimum value of VIH: 0.75 x SIM_VDD Maximum value of VOL: 0.15 x SIM_VDD Minimum value of VOH: 0.85 x SIM_VDD

N/A

SIM_RST

SIM card reset signal

I/O

Maximum value of VOL: 0.15 x SIM_VDD Minimum value of VOH: 0.85 x SIM_VDD

N/A

SIM_CLK

SIM card clock signal

I/O

Maximum value of VOL: 0.15 x SIM_VDD Minimum value of VOH: 0.85 x SIM_VDD

N/A

SIM_VDD

SIM card power signal

1.8

N/A

RESET

Used to reset the NM1 module, which is active at low level

N/A

NETLIGHT

Network status indication

N/A

RXD

Primary serial interface that receives data

1.8

N/A

TXD

Primary serial interface that transmits data

1.8

N/A

PSM_EINT

External interrupt pin, which is used to wake up the NM1 module from the PSM mode

N/A

SRCLKENAI

NFC interface

N/A

1.8

N/A

USB_DP

USB+ signal

N/A

USB_DM

USB– signal

N/A

USB_EINT

N/A

VIO18_EXT

1.8 V output power (In PSM mode, no voltage is output.)

Vmin = 1.53 V Vnorm = 1.8 V

N/A

DVDD_IO

N/A

GND

N/A

UART1_RXD

Auxiliary serial interface that receives data

1.8

N/A

UART1_TXD

Auxiliary serial interface that transmits data

1.8

N/A

UART1_CTS

Determines whether data is received.

N/A

1.8

N/A

UART1_RTS

Determines whether data is transmitted.

N/A

1.8

N/A

I2C0_SDA

I2C0 data

I/O

N/A

I2C0_SCL

I2C0 clock

N/A

GND

N/A

RF_ANT

RF antenna

Characteristic impedance of 50 ohms

GND

N/A

GND

N/A

RXD_DBG

Debugging serial interface that receives data

1.8

N/A

TXD_DBG

Debugging serial interface that transmits data

1.8

N/A

GND

N/A

GND

N/A

VSYS_BB

Input power

Vmin = 2.1 V Vnorm = 3.3 V Vmax = 3.63 V

N/A

VBAT_BOOST

Input power

Vmin = 2.1 V Vnorm = 3.3 V Vmax = 3.63 V

N/A

VSYS_PA

Output power

3.3

N/A

GPIO11

Reserved

N/A

1.8

N/A

GPIO10

Reserved

N/A

1.8

N/A

GPIO25

Reserved

N/A

1.8

N/A

MD_WAKEUP

N/A

GPIO28

Reserved

N/A

1.8

N/A

AP_READY

N/A

STATUS

N/A

GPIO24

Reserved

N/A

1.8

N/A

GPIO34

Reserved

N/A

1.8

N/A

GPIO33

Reserved

N/A

1.8

N/A

GPIO21

Reserved

N/A

1.8

N/A

GPIO20

Reserved

N/A

1.8

N/A

GPIO8

Reserved

N/A

1.8

N/A

GPIO1

Reserved

N/A

1.8

N/A

GPIO19

Reserved

N/A

1.8

N/A

RTC_GPIO0

N/A

SIM_DET

GPIO35

N/A

SIM card detection

N/A

GPIO32

Reserved

N/A

1.8

N/A

AVDD33_VUSB

N/A

FREF

Base frequency

N/A

GPIO31

N/A

1.8

N/A

GND

N/A

Electrical Conditions

Table 3-3 Electrical conditions

Signal

Description

Minimum Value

Typical Value

Maximum Value

Unit

VBAT_BOOST

Input power

2.1

3.3

3.63

VSYS_BB

Input power

2.1

3.3

3.63

VSYS_PA

Output power

N/A

3.3

N/A

Power Interface

Power Pins and Grounding

The NM1 module can be powered by a battery or external power supply. The GND signal pins indicate the power ground and signal ground of the NM1 module and need to be connected to the ground of the PCB . Improper connections of the GND signal pins may have adverse impact on the NM1 module performance.

Power Supply Requirements

The NM1 module's power design is important to its performance. The NM1 module can be powered by the low dropout regulator (LDO) with low static current and output current (up to 0.5 A) or the Li MnO2 battery. The input voltage range is from 2.1 V to 3.63 V. During data transmission, the power cannot be lower than the minimum working voltage 2.1 V. Otherwise, errors will occur. To ensure better power supply performance, it is recommended that three 47 µF (0805) ceramic capacitors and100 nF, 100 pF, and 22 pF (0402) filter capacitors be connected in parallel at the VBAT input end of the module. In addition, it is recommended that a TVS tube be connected to the VBAT input end to enhance the surge voltage bearing capability of the module. In principle, a longer VBAT cable leads to a larger trace width. Figure 3 2 shows the reference circuit.

SIM Card Interface

Pins

Table 3-4 Definition and description of SIM card interface signals

Pin No.

Signal Name

Signal Definition

Remarks

SIM_DATA

SIM card data pin

Voltage precision: 1.8 V±5% Maximum current: about 60 mA

SIM_CLK

SIM card clock pin

Voltage precision: 1.8 V±5% Maximum current: about 60 mA

SIM_RST

SIM card reset pin

Voltage precision: 1.8 V±5% Maximum current: about 60 mA

SIM_VDD

SIM card power supply pin

Voltage precision: 1.8 V±5% Maximum current: about 60 mA

SIM Card Interface Application

To ensure a better external SIM card performance and prevent the external SIM card being damaged, design the SIM card interface circuit in compliance with the following rules:

1）Place the external SIM card holder near the NM1 module. The external SIM card signal cable is 200 mm or shorter and is away from the RF cable and VBAT power cable.

2）The SIM_VDD decoupling capacitance does not exceed 1 μF, and the capacitor is near the external SIM card holder.

3）To prevent interference, keep the SIM_CLK and SIM_DATA signal cables at a certain distance from each other and use a ground cable to separate them

4）Connect the SIM_RST signal cable to the ground. To ensure a better ESD performance, you are advised to use TVS tubes to protect the pins of the external SIM card holder. The parasitic capacitance of the TVS tubes cannot be greater than 50 pF. Place ESD components near the external SIM card holder. Route the external SIM card signal cable from the external SIM card holder to the NM1 module through the ESD components.

SPIs

Pins

Table 3-7 defines the SPI signals. (SPIs support the slave mode.)

Table 3-5 SPI signal definition

Pin No.

Signal Name

Function Description

SPI_MISO

Master input and slave output

SPI_MOSI

Master output and slave input

SPI_ SCLK

SPI clock signal

SPI_CS

SPI selection signal

SPI Electrical Parameters and application

The level of the SPI on the NM1 module is 1.8 V. If the host level is 3.3 V, add a level converter between the NM1 module and host. The level converter that supports the SPI data rate is recommended. Figure 3 4 shows the reference circuit.

I2C Interface

Pins

Table 3-6 I2C interface signal definition

Pin No.

Signal Name

Function Description

SDA

I2C serial data

SCL

I2C serial clock

I2C is a two line bus for communication between ICs. It has a serial data cable (SDA) and a serial clock cable (SCL) to transmit information between connected devices. I 2 C identifies each device based on its unique address and can be used as both a transmitter and a receiver.

I2C Interface Electrical Parameters and application

UART Interface

Pins

The NM1 module provides three UART interfaces. The primary serial interface can be used for firmware upgrade. The default baud rate is 115.2 kbit/s, and the downloading baud rate is 921.6 kbit/s. You can use a log viewing tool to view logs over the debugging serial interface to debug software.

Table 3-7 UART interface signal definition

Pin No.

Signal Name

Function Description

RXD

Data receiving over the primary serial interface

TXD

Data transmission over the primary serial interface

UART1_RXD

Data receiving over the auxiliary serial interface

UART1_TXD

Data transmission over the auxiliary serial interface

RXD_DBG

Data receiving over the debugging serial interface

TXD_DBG

Data transmission over the debugging serial interface

UART Interface Electrical Parameters and application

Figure 3-6 Reference circuit

The level of the UART interfaces on the NM1 module is 1.8 V. If the application system level is 3.3 V, add a level converter to the connection between the NM1 module and application system over the serial interface. Figure 3 7 shows the reference circuit with a level converter, UM3202.

A triode can also be used for level conversion.

Note: Connection methods of the debugging, auxiliary, and primary serial interfaces are similar.

USB Interface

Pins

The NM1 module has a USB 1.1 interface, which can only be used for module upgrade. If ESD design is required, the maximum capacitance of ESD components must be less than 0.5 pF. Otherwise, waveform distortion may occur, affecting bus communication. The differential impedance of differential data cables must be within 90 ohms.

Table 3-8 USB inte rface signal definition

Pin No.

Signal Name

Function Description

RXD

Receiving over the serial interface

TXD

Transmission over the serial interface

USB_DP

USB+ signal

USB_DM

USB– signal

AVDD33_VUSB

Internal USB power supply

USB Interface Application

The nominated input power of the NM1 module is 3.3 V. When the USB interface is used for downloading, add an LDO circuit to keep t he circuit voltage at 3.3 V.

Power On/Power Off and Reset Interface

PWRKEY Pin

Table 3-9 PWRKEY signal definition

Pin No.

Signal Name

Function Description

PWRKEY

NM1 module power-on

Power On/Power Off Interface application

To power on the NM1 module, lower the PWRKEY pin to a low level for a period of time and then disconnect it or raise it to a high level.

RESET Pin

Pin No.

Signal Name

Function Description

RESET

NM1 module resetting

To reset the NM1 module, lower the RESET pin to a low level for a period of time and then disconnect it or raise it to a high level.

RESET Interface Application

Design Instructions

This chapter provides general design guidance about the NM1 module to ensure a better product performance.

General Design Rules and Requirements

During peripheral circuit design, ensure that the external power supply have sufficient power and the differential impedance of the USB 1.1 signa l cable is within 90 ohms. Design general signal interfaces as required to match the interface signal level and prevent the NM1 module being damaged due to inconsistent levels. The NM1 module has good RF indicator performance. You need to design the antenna circuit on the PCB as required and control the impedance to prevent the RF indicators being affected.

Power Supply Circuit Design

The power supply on the PCB should supply 0.5 A or higher power to meet peak current requirements of the NM1 module. The trace width on the PCB must be large enough and form good circulation with the ground. In addition, add a large capacitor with over 1000 μF to the power supply circuit to ensure transient power supply, and control the power ripple within 100 mV.

RF Circuit Design

GND

N/A

RF_ANT

RF antenna

50 ohms characteristic impedance

GND

N/A

GND

N/A

RF Antenna Circuit Design

It is recommended that a πtype matching circuit be reserved during RF antenna per ipheral circuit design. Ensure that the matching circuit is near the antenna, and attach resistors based on actual debugging conditions.By default, no resistor is attached to C1 and C2, and a 0 ohms resistor is attached to R1. The RF antenna peripheral circuit must have 50 ohms impedance. In the recommended RF antenna peripheral circuit layout solution, the RF cable is routed at layer 1 and the reference cable at layer 2. Use the Shortcut to Si9000 software to calculate the PCB cable impedance of the RF antenna. Figure 4 1 shows a model. During PCB cabling design, ensure that the RF reference point is complete.

During impedance calculation, specify parameters shown in Figure 4 2 and change the RF trace width to obtain the required impedance value. For typical antennas, 50 ohm impedance is recommended.

Precautions for Initial Antenna Design

Pre-project Evaluation

Ensure that the antenna is horizontal with the base station for maximum efficiency. Do not place the antenna near the power cable, data cable, or chip that may generate electromagnetic interference. Do not reserve a place for hands on the antenna to prevent attenuation caused by the human body. Consider radiation reduction and structure implementation. In the initial design phase, th e structure, ID, circuit, and antenna engineers evaluate the antenna layout together.

Antenna Matching Circuit

If a long cable exists between the RF and antenna interfaces on the NM1 module, design 50 ohms characteristics impedance for the microstrip or stripline between the RF pad and the antenna interface during PCB circuit design. In addition, reserve a matching circuit.

Suggestions on EMC and ESD Design

During overall design, consider EMC issues related to signal integrity and power integrity. During peripheral circuit cabling of the NM1 module, reserve doubled trace width between the power cable and signal cable to reduce signal coupling and ensure pure return current. During peripheral power circuit design, place the decoupling capacitor near the power pin on the NM1 module, keep high frequency and high speed circuits and sensitive circuits away from the PCB edges, and isolate the circuits from each other to reduce interference. Protect sensitive signals, and shield circuits or components on the PCB that may interfere the NM1 module. Consider ESD protection during design. Place ESD components near the key input and output signal interfaces, for example, the SIM card signal interface, to protect them. On the PCB , reasonably design mechanical p arts and PCB layout and ensure proper grounding of metal shielding covers to provide a smooth channel for static electricity discharging.

PCB Solder Pad Design

You are advised to design the middle 14 pads on the PCB based on the sizes in the structure diagram. Externally extend the 52 signal pads around the PCB to the NM1 module for over 0.3 mm, and externally extend other three sides of the pads for 0.05 mm. Use 50 ohms impedance cables for the main antenna and Wi Fi antenna.

Thermal Design

The NM1 module generates heat when it works and may be affected by other high temperature components. TheNM1 module design ensures good heat dissipation. When connecting the NM1 module to the PCB , properly connect the thermal pad to the ground to ensure thermal conduction and balance and a better electrical performance. Note:

1）Place the NM1 module away from the power supply and high speed signal cables, and protect these cables.

2）Place the antenna and the coaxial cable that is used to connect the antenna and NICPlace the antenna and the coaxial cable that is used to connect the antenna and NIC away from these away from these interference sources. interference sources.

3）Place the NM1 module away from components that generate a large amount of heat such as the CPU to prevent Place the NM1 module away from components that generate a large amount of heat such as the CPU to prevent the RF performance being affected by high temperature.the RF performance being affected by high temperature.

Production Instructions

Stencil Design

During stencil design, note the following: 1） When making the stencil of the thermal pad at the bottom of the NM1 module, reduce the stencil opening by 25% to reduce short circuits between the thermal pad and functional pins around the NM1 module. 2）To ensure better solde ring, use step stencils. 3）Use a diagonal opening for the stencil of the thermal pad. Figure 5 1 shows recommended stencil strips.

Oven Temperature Curve

The oven temperature curve has great impact on the soldering quality and material status. When the temperature rises from the ambient temperature to 150°C, the rising speed is less than 3°C per second. A temperature higher than 217°C is allowed for a maximum of 70s, and 55s is recommended. Otherwise, some components may be invalid due to strong thermal attacks, resulting in a higher defect rate and more repair difficulty. The highest temperature cannot exceed 245°C. Some materials such as the crystal may have die cracks at a high temperature. As a result, the crystal does not work and the module functions are affected. Table 5 1 describes the oven temperature curve parameter settings, and Figure 5 2 shows the oven temperature curves.

Lead-free Oven Temperature Curve

Phase

Temperature

Description

Preheating

From the ambient temperature to 150°C

Rising speed: < 3°C per second

Heat preservation

150°C to 200°C

Duration: 40s to 110s

Soldering

> 217°C