Hardware User Guide
Issue 1.2 Date 2020-09-18
N27 Hardware User Guide
Copyright
Copyright © Neoway Technology Co., Ltd
i
Copyright © Neoway Technology Co., Ltd 2020. All rights reserved.
No part of this document may be reproduced or transmitted in any form or by any means without prior written
consent of Neoway Technology Co., Ltd.
is the trademark of Neoway Technology Co., Ltd.
All other trademarks and trade names mentioned in this document are the property of their respective
holders.
Notice
This document provides a guide for users to use N27.
This document is intended for system engineers (SEs), development engineers, and test engineers.
THIS GUIDE PROVIDES INSTRUCTIONS FOR CUSTOMERS TO DESIGN THEIR APPLICATIONS.
PLEASE FOLLOW THE RULES AND PARAMETERS IN THIS GUIDE TO DESIGN AND COMMISSION.
NEOWAY WILL NOT TAKE ANY RESPONSIBILITY OF BODILY HURT OR ASSET LOSS CAUSED BY
IMPROPER OPERATIONS.
THE INFORMATION IN THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE DUE TO
PRODUCT VERSION UPDATE OR OTHER REASONS.
EVERY EFFORT HAS BEEN MADE IN PREPARATION OF THIS DOCUMENT TO ENSURE ACCURACY
OF THE CONTENTS, BUT ALL STATEMENTS, INFORMATION, AND RECOMMENDATIONS IN THIS
DOCUMENT DO NOT CONSTITUTE A WARRANTY OF ANY KIND, EXPRESS OR IMPLIED.
Neoway provides customers complete technical support. If you have any question, please contact your
account manager or email to the following email addresses:
Website: http://www.neoway.com
N27 Hardware User Guide
Contents
Copyright © Neoway Technology Co., Ltd
ii
Contents
1 About N27 .................................................................................................. 9
1.1 Product Overview ......................................................................................................................... 9
1.2 Block Diagram .............................................................................................................................. 9
1.3 Basic Features ........................................................................................................................... 10
2 Module Pins ............................................................................................. 12
2.1 Pad Layout ................................................................................................................................. 12
2.2 Pin Description ........................................................................................................................... 13
3 Application Interfaces .............................................................................. 18
3.1 Power Interface .......................................................................................................................... 18
3.1.1 VBAT .................................................................................................................................. 18
3.1.2 VDDIO_1P8 ....................................................................................................................... 20
3.2 Control Interfaces ....................................................................................................................... 20
3.2.1 PWRKEY_N ...................................................................................................................... 20
3.3 Peripheral Interfaces .................................................................................................................. 22
3.3.1 USB ................................................................................................................................... 22
3.3.2 UART ................................................................................................................................. 23
3.3.3 SIM .................................................................................................................................... 25
3.3.4 PCM ................................................................................................................................... 26
3.3.5 SPI ..................................................................................................................................... 29
3.3.6 I2C ..................................................................................................................................... 30
3.4 RF Interface ................................................................................................................................ 31
3.4.1 ANT Interface ..................................................................................................................... 31
3.4.2 ANT_GNSS Interface ........................................................................................................ 33
3.4.3 Antenna Assembling .......................................................................................................... 34
3.5 LCD* Interfaces .......................................................................................................................... 36
3.6 Other Interfaces ......................................................................................................................... 36
3.6.1 ADC ................................................................................................................................... 36
3.6.2 USB_BOOT ....................................................................................................................... 37
3.6.3 STATUS ............................................................................................................................. 37
3.6.4 NET_LIGHT ....................................................................................................................... 37
4 Electric Features and Reliability .............................................................. 38
4.1 Electric Features ........................................................................................................................ 38
4.2 Temperature Features ................................................................................................................ 39
4.3 ESD Protection ........................................................................................................................... 39
5 RF Features ............................................................................................. 40
5.1 Operating Bands ........................................................................................................................ 40
5.2 TX Power and RX Sensitivity ..................................................................................................... 41
5.3 GNSS Feature ............................................................................................................................ 44
6 Mechanical Features ............................................................................... 45
N27 Hardware User Guide
Contents
Copyright © Neoway Technology Co., Ltd
iii
6.1 Dimensions ................................................................................................................................. 45
6.2 Label ........................................................................................................................................... 46
6.3 Packing ....................................................................................................................................... 46
6.3.1 Packaging .......................................................................................................................... 46
6.3.2 Moisture ............................................................................................................................. 46
7 Mounting N27 onto Application PCB ....................................................... 47
7.1 Bottom Dimensions .................................................................................................................... 47
7.2 Application Foot Print ................................................................................................................. 48
7.3 Stencil ......................................................................................................................................... 48
7.4 Solder Paste ............................................................................................................................... 48
7.5 SMT Furnace Temperature Curve .............................................................................................. 49
8 Safety Recommendations ....................................................................... 50
Conformity and Compliance .................................................................... 51
A.1 Approvals ................................................................................................................................... 51
A.2 Chinese Notice........................................................................................................................... 51
A.2.1 CCC Class A Digital Device Notice ................................................................................... 51
A.2.2 Environmental Protection Notice ....................................................................................... 51
A.3 American Notice ......................................................................................................................... 51
A.3.1 Modify ................................................................................................................................ 51
A.3.2 FCC Class A Digital Device Notice ................................................................................... 51
A.3.3 FCC Class B Digital Device Notice ................................................................................... 52
Abbreviation ............................................................................................ 53
N27 Hardware User Guide
Table of Figures
Copyright © Neoway Technology Co., Ltd
iv
Table of Figures
Figure 1-1 Block Diagram ................................................................................................................ 10
Figure 2-1 N27 Pin definition ............................................................................................................ 12
Figure 3-1 Recommended power design ......................................................................................... 18
Figure 3-2 Reference design of startup controlled by button ........................................................... 20
Figure 3-3 Reference design of startup controlled by MCU ............................................................. 20
Figure 3-4 Startup timing .................................................................................................................. 21
Figure 3-5 Shutdown timing ............................................................................................................. 21
Figure 3-6 USB connection .............................................................................................................. 22
Figure 3-7 UART connection ............................................................................................................ 24
Figure 3-8 Recommended level shifting network ............................................................................. 24
Figure 3-9 Reference design of the SIM card interface ................................................................... 25
Figure 3-10 PCM connection ........................................................................................................... 26
Figure 3-11 PCM sync signal timing ................................................................................................. 27
Figure 3-12 PCM data input timing .................................................................................................. 27
Figure 3-13 PCM data output timing ................................................................................................ 27
Figure 3-14 I2Sconnection ............................................................................................................... 28
Figure 3-15 I2S timing ...................................................................................................................... 29
Figure 3-16 SPI connection .............................................................................................................. 30
Figure 3-17 SPI timing ..................................................................................................................... 30
Figure 3-18 Pi network ..................................................................................................................... 32
Figure 3-19 Recommended RF PCB design ................................................................................... 32
Figure 3-20 GNSS RF structure ....................................................................................................... 33
Figure 3-21 Specifications of MM9329-2700RA1 ............................................................................ 34
Figure 3-22 RF connections ............................................................................................................. 34
Figure 3-23 Antenna layout .............................................................................................................. 35
Figure 3-24 Layout around the antenna ........................................................................................... 35
Figure 3-25 Reference design of USB_BOOT ................................................................................. 37
N27 Hardware User Guide
Table of Figures
Copyright © Neoway Technology Co., Ltd
v
Figure 6-1 N27 dimensions (Unit: mm) ............................................................................................ 45
Figure 7-1 Bottom dimensions of N27 (Unit: mm) ............................................................................ 47
Figure 7-2 Recommended footprint of N27 application PCB (Unit: mm) ......................................... 48
Figure 7-3 SMT furnace temperature curve ..................................................................................... 49
N27 Hardware User Guide
Table of Tables
Copyright © Neoway Technology Co., Ltd
vi
Table of Tables
Table 1-1 Variant and frequency bands .............................................................................................. 9
Table 2-1 IO definition ...................................................................................................................... 13
Table 2-2 Pin description .................................................................................................................. 13
Table 3-1 Timing parameters of PCM interface ................................................................................ 27
Table 3-2 Timing parameters of I2S interface .................................................................................. 29
Table 3-3 Timing parameters of SPI interface .................................................................................. 30
Table 4-1 Operating conditions of N27 ............................................................................................. 38
Table 4-2 Current consumption of N27 (typical) ............................................................................... 38
Table 4-3 Temperature feature of N27 ............................................................................................. 39
Table 4-4 ESD protection of N27 ...................................................................................................... 39
Table 5-1 Operating Bands of N27 ................................................................................................... 40
Table 5-2 RF transmit power of N27 ................................................................................................ 41
Table 5-3 RX sensitivity of N27 GSM ............................................................................................... 42
Table 5-4 RX sensitivity of N27 Cat M1 ........................................................................................... 42
Table 5-5 RX sensitivity of N27 Cat NB1 (without retransmission) .................................................. 43
Table 5-6 RX sensitivity of N27 Cat NB1 (with retransmission) ....................................................... 43
N27 Hardware User Guide
About This Document
Copyright © Neoway Technology Co., Ltd
vii
About This Document
Scope
This document is applicable to N27 series.
It defines the features, indicators, and test standards of the N27 module and provides reference for the
hardware design of each interface.
Audience
This document is intended for system engineers (SEs), development engineers, and test engineers.
Change History
Issue
Date
Change
Changed By
1.0
2019-12
Initial draft
Longsigh Huang
1.1
2020-04
⚫ Modified the variants
⚫ Updated the currents
⚫ Updated GNSS features
Longsigh Huang
1.2
2020-09
⚫ Updated the variants and bands and deleted B14
from all variants.
⚫ Added B72 and B73 to N27-W1
⚫ Deleted N27-W2
⚫ Updated the temperature parameter
Longsigh Huang
N27 Hardware User Guide
About This Document
Copyright © Neoway Technology Co., Ltd
viii
Conventions
Symbol
Indication
This warning symbol means danger. You are in a situation that could cause fatal
device damage or even bodily damage.
Means reader be careful. In this situation, you might perform an action that could
result in module or product damages.
Means note or tips for readers to use the module
Related Documents
Neoway_N27_Datasheet
Neoway_N27_Product_Specifications
Neoway_N27_AT_Command_Mannual
Neoway_N27_EVK_User_Guide
N27 Hardware User Guide
Chapter 1 About N27
Copyright © Neoway Technology Co., Ltd
9
1 About N27
N27 is an industrial-grade LTE-Cat M/Cat NB1/Cat NB2 module that is developed on Qualcomm
MDM9205 and supports FDD LTE, GPRS, and GPS.
1.1 Product Overview
The N27 series includes multiple variants. The following table lists the variants and frequency bands
supported. * indicates that the variant or function is in the development phase.
Table 1-1 Variant and frequency bands
Variant
Category
Band
GNSS
W3
Cat M1/
GPRS
Cat M1: B1, B2, B3, B4, B5, B8, B12, B13, B18, B19, B20,
B25, B26, B27, B28, B66, B85
GPRS: 850/900/1800/1900 MHz
Support
W1*
Cat M1/Cat NB1/
Cat NB2
GPRS
Cat M1: B1, B2, B3, B4, B5, B8, B12, B13, B18, B19, B20,
B25, B26, B27, B28, B31, B66, B72,B73, B85
CATNB1/NB2: B1, B2, B3, B4, B5, B8, B12, B13, B18, B19,
B20, B25, B26, B28, B31, B66, B72,B73, B85
GPRS: 850/900/1800/1900 MHz
Support
WW*
Cat M1/Cat NB1/
Cat NB2
GPRS
Cat M1: B1, B2, B3, B4, B5, B8, B12, B13, B18, B19, B20,
B25, B26, B27, B28, B66, B85
Cat NB1/NB2: B1, B2, B3, B4, B5, B8, B12, B13, B18, B19,
B20, B25, B26, B28, B66, B71, B85
GPRS: 850/900/1800/1900 MHz
Support
N27 adopts a 76-pin package with a square GND pad at each corner. Its dimensions are only 18 mm
x24 mm. With industrial-grade performance, it is well applicable to electrical terminals, tracker, POS,
and other IoT terminals.
1.2 Block Diagram
N27 consists of the following functionality units:
⚫ Baseband
⚫ Internal memory
N27 Hardware User Guide
Chapter 1 About N27
Copyright © Neoway Technology Co., Ltd
10
⚫ 19.2MHz crystal oscillator
⚫ Power management unit
⚫ RF section
⚫ Digital interfaces (SIM, I2C, UART, PCM*, USB, LCD, SPI)
⚫ Analog interfaces (ADC)
Figure 1-1 Block Diagram
Power
Manager
Baseband+Internal memory
MDM9205
RF Front-end-
module
Interface
SIM
VBAT RF transceiver
SDR105
19.2MHz
I2C
SDI
O
SPI
UAR
T
USB GPI
OLCDUART SPI PCM
ADC
* indicates the function is in the development phase.
1.3 Basic Features
Parameter
Description
Physical features
⚫ Dimensions: (24.0±0.15) mm × (18.0±0.15) mm × (2.3±0.2) mm
⚫ Package: LGA
⚫ Weight: 2.4g
N27 Hardware User Guide
Chapter 1 About N27
Copyright © Neoway Technology Co., Ltd
11
Temperature ranges
Operating: -40°C to +85°C 1
Storage: -40°C to +90°C
Operating voltage
VBAT: 3.1V to 4.3V, TYP: 3.6V
Current
PSM: < 4 μA
Idle: < 2 mA
Working: 250 mA@ Cat M
MIPS processor
ARM Cortex-A7 processor, 800 MHz main frequency, 256 KB L2 cache
Memory
32 MB LPDDR2 + 64MB NAND Flash
Band
See Table 1-1.
Wireless rate
GPRS: Max 85.6 Kbit/s(DL) / Max 85.6 Kbit/s(UL)
FDD LTE:
Cat M1, Max 588Kbps(DL)/Max 1.119Mbps(UL)
Cat NB1, Max 34Kbps(DL)/Max 19.7(single-tone)/66.6(multi-tone)Kbps(UL)
Cat NB2, Max 127Kbps(DL)/Max 158.5Kbps(UL)
Transmit power
EGSM900: +33dBm (Power Class 4)
DCS1800: +30dBm (Power Class 1)
LTE CAT-M/CAT-NB: +23dBm (Power Class 3)
Application
interfaces
2G/4G antenna, GNSS antenna, 50Ω characteristic impedance
Three UART interfaces, at most 4 Mbit/s
One SIM interface, 1.8V only
One USB2.0 interface, device mode only
Two ADC interfaces, detectable voltage ranging from 0.1 to 1.7V
One I2C interface, master mode only
One SPI interface, maximum frequency of 50 MHz
One PCM interface, MUX as I2S interface
One LCD interface, in development phrase
AT commands
3GPP Release 13
Neoway extended commands
SMS
PDU, TXT
Protocol
TCP, UDP, HTTP, FTP, MQTT, LWM2M, COAP
Certification approval
CCC, FCC, RoSH
1
Some RF indicators might not meet 3GPP/3GPP2 standards in extended temperature but it does not affect
functioning.
N27 Hardware User Guide
Chapter 2 Module Pins
Copyright © Neoway Technology Co., Ltd
12
2 Module Pins
There are 76 pins on N27 and their pads are introduced in the LGA package.
2.1 Pad Layout
Figure 2-1 shows the pad layout of the N27.
Figure 2-1 N27 Pin definition
13
2
3
4
5
6
7
8
9
10
11
12
74
1
UART0_RXD
UART0_TXD
VDDIO_1P8
GND
LCD_TE
LCD_OE_N
LCD_WE_N
LCD_A_0
LCD_A_1
LCD_A_2
LCD_A_3
LCD_A_4
LCD_A_5
GND
VBAT
VBAT
GND
USIM_PRESENT
USIM_VCC
USIM_DATA
USIM_CLK
USIM_RESET
GND
I2C_SDA
I2C_SCL
UART2_TXD
73
16
17
18
19
20
21
15
PCM_SYNC
PCM_DIN
PCM_DOUT
PCM_CLK
I2S_MCLK
ADC1
ADC0
14
UART2_RXD
22
23
24
25
26
27
28
29
30
32
31
UART1_RTS
UART1_TXD
GND
UART1_CTS
UART1_RXD
USB_VDD_3P3_EN
USB_VDD_3P3
USB_VBUS
USB_DM
USB_DP
GND
33
34
36
35
USB_BOOT
LCD_A_8
LCD_A_7
LCD_A_6
45
56
55
54
53
52
51
50
49
48
47
46
75
57
76
42
41
40
39
38
37
43
44
UART0_CTS
UART0_RTS
PWRKEY_N
RESERVED
WAKEUP_IN
WAKEUP_OUT
STATUS
NET_LIGHT
72
71
70
69
68
67
66
65
64
62
63
61
60
58
59
ANT_GNSS
1PPS
GND
GND
GNSS_LNA_EN
GND
SPI_MOSI
SPI_MISO
SPI_CLK
SPI_CS_N
LCD_RESET_N
LCD_CS_N
GND
ANT
GND
N27
Top View
GND
GND
GND GND
N27 Hardware User Guide
Chapter 2 Module Pins
Copyright © Neoway Technology Co., Ltd
13
2.2 Pin Description
Table 3-1 lists the definition of IO types
Table 2-1 IO definition
IO Type
B
Digital input/output, COMS logic level
DO
Digital output, COMS logic level
DI
Digital input, COMS logic level
PO
Power output
PI
Power input
AO
Analog output
AI
Analog input
AIO
Analog input/output
Level Feature
P3
1.8V digital IO power domain
VIH min=1.2V, VIL max= 0.3V
VOH min=1.35V, VOLmax=0.45V
P4
3.3V power supply of USB_PHY core
Vtyp=3.3V
Table 2-2 Pin description
Signal
Pin
I/O
Function
Level
Feature
Remarks
Power interface
VBAT
2, 3
PI
Main power
input
Vmin=3.1V,
Vmax=4.3V,
Vtyp=3.6V
Peak current is up to 3A
VDDIO_1P8
47
PO
1.8V power
output
Vnorm=1.8V
Imax=50 mA
Used only for level shifting and
IO power supply.
Leave this pin floating if it is not
used.
GND
1, 4, 10, 22, 32, 46, 58, 60, 67, 70, 72, 73, 74,
75, 76
Ensure that all GND pins are
connected to the ground plane
Control Interfaces
PWRKEY_N
52
DI
ON/OFF button
P3
Connected to 1.8V through an
internal pull-up resistor
Used to control the module
N27 Hardware User Guide
Chapter 2 Module Pins
Copyright © Neoway Technology Co., Ltd
14
startup, shutdown, and
wakeup from PSM.
STATUS
56
DO
Startup indicator
P3
Used to indicate the startup
status of the module
Leave this pin floating if it is not
used.
NET_LIGHT
57
DO
Network status
indicator
P3
Leave this pin floating if it is not
used.
WAKEUP_OUT
55
DO
Wake up the
device
P3
Leave this pin floating if it is not
used.
UART0 Interface
UART0_TXD
48
DO
Data TX
P3
Used for data transmission.
Leave these pins floating if
they are not used.
UART0_RXD
49
DI
Data RX
P3
UART0_CTS
50
DI
Clear to send
P3
Leave this pin floating if it is not
used.
UART0_RTS
51
DO
Request to send
P3
Leave this pin floating if it is not
used.
UART1 port
UART1_RTS
23
DO
Request to send
P3
Leave this pin floating if it is not
used.
UART1_CTS
24
DI
Clear to send
P3
Leave this pin floating if it is not
used.
UART1_RXD
25
DI
Data RX
P3
Used for data transmission.
Leave these pins floating if
they are not used.
UART1_TXD
26
DO
Data TX
P3
UART2 port
UART2_TXD2
13
DO
Data TX
P3
Used for data transmission.
Leave these pins floating if
they are not used.
UART2_RXD
14
DI
Data RX
P3
SIM Interface
USIM_VCC
6
PO
SIM card power
supply output
Support 1.8V only, IOmax
=30mA
USIM_DATA
7
B
SIM card data IO
P3
Connect it to USIM_VCC
through a 10 kΩ pull-up
resistor.
USIM_CLK
8
DO
SIM card clock
P3
USIM_RESET
9
DO
SIM card reset
P3
N27 Hardware User Guide
Chapter 2 Module Pins
Copyright © Neoway Technology Co., Ltd
15
USIM_PRESENT
5
DI
SIM detect
P3
USB interface
USB_VBUS
29
PI
Charging
voltage check
4.75V~5.25
V
TYP: 5.0V
The interface complies with the
USB2.0 standard.
USB_DM
30
AIO
USB data
negative signal
USB_DP
31
AIO
USB data
positive signal
USB_VDD_3P3
28
PO
Power supply for
the USB_PHY
P4
Do NOT use it.
Leave this pin floating.
USB_VDD_3P3_
EN
27
B
P3
Reserved
Leave this pin floating.
ADC interface
ADC0
20
AI
Analog-to-digital
signal
conversion
Vmax=1.7V;
Vmin=0.1V
15-bit, detectable voltage
ranging from 0.1V to 1.7V
Leave this pin floating if it is not
used.
ADC1
21
AI
Analog-to-digital
signal
conversion
Vmax=1.7V;
Vmin=0.1V
15-bit, detectable voltage
ranging from 0.1V to 1.7V
Leave this pin floating if it is not
used.
I2C interface
I2C_SCL
12
B
I2C clock
P3
Connect it to 1.8V through an
external 2.2 kΩ pull-up
resistor. Leave this pin floating
if it is not used.
I2C_SDA
11
B
I2C data
P3
PCM interface
PCM_SYNC
15
B
PCM
synchronous
signal
P3
Multiplexed as I2S_WS
PCM_DIN
16
DI
PCM data RX
P3
Multiplexed as I2S_RX
PCM_DOUT
17
DO
PCM data TX
P3
Multiplexed as I2S_TX
PCM_CLK
18
DO
PCM clock
signal
P3
Multiplexed as I2S_SCLK
I2S_MCLK
19
DO
I2S main clock
P3
SPI interface
SPI_CLK
64
DO
Clock signal
P3
Leave this pin floating if it is not
N27 Hardware User Guide
Chapter 2 Module Pins
Copyright © Neoway Technology Co., Ltd
16
used.
SPI_MISO
65
DI
Slave output,
master input
P3
Leave this pin floating if it is not
used.
SPI_MOSI
66
DO
Slave input,
master output
P3
Leave this pin floating if it is not
used.
SPI_CS_N
63
DO
Chip select
P3
Leave this pin floating if it is not
used.
LCD*
LCD_A_D0
42
B
P3
LCD is in the development
phase.
Its pins can be multiplexed as
GPIOs.
LCD_A_D12
41
B
P3
LCD_A_D2
40
B
P3
LCD_A_D3
39
B
P3
LCD_A_D4
38
B
P3
LCD_A_D5
37
B
With interrupt
P3
LCD_A_D6
36
B
P3
LCD_A_D72
35
B
P3
LCD_A_D8
34
B
P3
LCD_WE_N
43
B
P3
LCD_OE_N
44
B
P3
LCD_TE
45
B
With interrupt
P3
LCD_CS_N
61
B
P3
LCD_RESET_N
62
B
With interrupt
P3
Antenna Interface
ANT_GNSS
71
AI
GNSS antenna
50Ω impedance for traces
ANT
59
AIO
Main antenna
50Ω impedance for traces
Other Interface
GNSS_LNA_EN2
69
DO
GNSS LNA
enable
P3
Leave this pin floating if it is not
used.
1PPS
68
DO
GNSS one pulse
per second
output
WAKEUP_IN*
54
DI
Reserved pin
P3
The function is in the
development phase.
Do NOT pull up these pins to high level or ground them before the module is started completely. otherwise, the
module cannot start up successfully.
N27 Hardware User Guide
Chapter 2 Module Pins
Copyright © Neoway Technology Co., Ltd
17
USB_BOOT
33
DI
Forcible
download
control
P3
Connect USB_BOOT to
VDDIO_1P8 through a pull-up
resistor before the module is
started, and the module will
enter forcible download mode.
RESERVED
53
/
Reserved pin
/
Leave it floating.
N27 Hardware User Guide
Chapter 3 Application Interfaces
Copyright © Neoway Technology Co., Ltd. All rights reserved.
18
3 Application Interfaces
N27 provides power supply, control, communications, RF, and other interfaces to meet customers'
requirements in different application scenarios.
This chapter describes how to design each interface and provides reference designs and guidelines.
3.1 Power Interface
Signal
Pin
I/O
Function
Remarks
VBAT
2, 3
PI
Main power input
3.1V~4.3V (TYP: 3.6V)
VDDIO_1P8
47
PO
1.8V power output
Max. 50 mA output, used only for level shifting.
Add TVS diode when using this pin.
GND
1, 4, 10, 22, 32, 46, 58, 60, 67, 70,
72, 73, 74, 75, 76
Ensure that all GND pins are connected to the
ground plane.
3.1.1 VBAT
The power supply design covers two parts: schematic design and PCB layout.
Schematic Design
Figure 3-1 shows the reference design of the N27 VRTC power supply.
Figure 3-1 Recommended power design
Power Supply N27 Module
D1 C1 C2 C3 C4
Close to the pin of the module
VBAT
Test point
I_max
C5
Schematic guidelines
N27 Hardware User Guide
Chapter 3 Application Interfaces
Copyright © Neoway Technology Co., Ltd. All rights reserved.
19
⚫ The maximum input voltage for the module is 4.3 V and the typical value is 3.6V.
⚫ The protection voltage at D1 should not exceed the maximum input voltage the module can bear.
Place TVS close to the input of the power supply to clamp the surge voltage before it enters
back-end circuits. Therefore, the back-end components and the module are protected.
⚫ A large bypass tantalum capacitor (220 μF or 100 μF) or aluminum capacitor (470 μF or 1000μF)
is expected at C1 to reduce voltage drops during bursts. Its safe operating voltage should be
larger than 1.5 times the voltage across the power supply.
⚫ Place a bypass capacitor of low-ESR close to the module to filter out high-frequency jamming
from the power supply.
PCB Layout
Place an ESR capacitor at the output of the power supply to absorb surge current. Place a TVS diode
at the input of VBAT to protect back-end components. Follow the rules below in the power supply
design:
⚫ TVS diodes dissipate the transient pulse power during a surge and can handle a peak pulse
current of dozens or more than 100 A. they have a fast response time.
Place the TVS as close to the interface as possible to ensure that the surge voltage can be
clamped before the pulse is coupled to the neighbor traces.
⚫ Place bypass capacitors close to the power pin of the module to filter out the high-frequency
signal from the power supply.
⚫ Ensure that the width of PCB traces for VBAT circuits allows 3A current and ensure no obvious
decrease of loop voltages.
The trace should be 3 mm in width at least and the ground plane should be as complete as
possible. The traces of the power circuit should be as short and wide as possible.
⚫ Place noise-sensitive circuits such as audio and RF far away from power supply circuits,
especially when the DC-DC is adopted in the design.
⚫ Connect GND pins and bottom pads to the ground to optimize heat sink and separate noise.
In GSM/GPRS mode, RF data is transmitted in burst mode that generates voltage drops on the power
supply. Furthermore, this results in a 216Hz TDD noise through the power and the transient peak current is up to
3A. Ensure low resistance of power supply trace in design to avoid voltage drop.
Never use a diode to make the drop voltage between a higher input and module power. Otherwise, Neoway
will not provide a warranty for product issues caused by this. In this situation, the diode will obviously decrease
the module performances, or result in unexpected restarts, due to the forward voltage of the diode will vary
greatly in different temperature and current. The module might not work properly with a diode power supply.
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