Quectel BC68 User manual

BC68&M66
Compatible Design
NB-IoT/GSM/GPRS Module Series
Rev. BC68&M66_Compatible_Design_V1.0
Date: 2018-03-22
Status: Released
www.quectel.com

NB-IoT/GSM/GPRS Module Series
BC68&M66 Compatible Design
BC68&M66_Compatible_Design 1 / 31
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BC68&M66 Compatible Design
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About the Document
History
Revision
Date
Author
Description
1.0
2018-03-22
Power JIN
Initial

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BC68&M66 Compatible Design
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Contents
About the Document...................................................................................................................................2
Contents.......................................................................................................................................................3
Table Index...................................................................................................................................................4
Figure Index.................................................................................................................................................5
1Introduction..........................................................................................................................................6
2General Descriptions...........................................................................................................................7
2.1. Product Description...................................................................................................................7
2.2. Features Overview....................................................................................................................8
2.3. Pin Assignment........................................................................................................................10
3Pin Description...................................................................................................................................11
4Hardware Reference Design.............................................................................................................14
4.1. Power Supply..........................................................................................................................14
4.1.1. Reference Design for Power Supply..............................................................................14
4.1.2. Reduce Voltage Drop.....................................................................................................14
4.2. Power-on Circuit......................................................................................................................15
4.3. Power-off Circuit......................................................................................................................16
4.3.1. Power down Module viaAT Command..........................................................................16
4.3.2. Power down M66 Using PWRKEY Pin..........................................................................17
4.4. Reset BC68.............................................................................................................................18
4.5. Network Status Indication........................................................................................................19
4.6. (U)SIM Interface......................................................................................................................19
4.7. UART Interfaces......................................................................................................................20
4.8. ADC Interface..........................................................................................................................21
4.9. RFAntenna Interface..............................................................................................................22
5Recommended Footprint and Stencil Design.................................................................................23
5.1. Recommended Compatible Footprint.....................................................................................23
5.2. Recommended Stencil Design................................................................................................25
5.3. Installation Sketch Map...........................................................................................................27
6Manufacturing and Packaging..........................................................................................................28
6.1. Soldering.................................................................................................................................28
6.2. Packaging................................................................................................................................29
6.2.1. BC68 and M66 Packaging.............................................................................................29
7Appendix A References.....................................................................................................................30

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Table Index
TABLE 1: MODULE GENERAL INFORMATION................................................................................................. 7
TABLE 2: FEATURES OVERVIEW ..................................................................................................................... 8
TABLE 3: I/O PARAMETERS DEFINITION........................................................................................................11
TABLE 4: PIN COMPARISON BETWEEN BC68 AND M66...............................................................................11
TABLE 5: UART INTERFACE VOLTAGE DOMAIN........................................................................................... 20
TABLE 6: RELATED DOCUMENTS.................................................................................................................. 30
TABLE 7: TERMS AND ABBREVIATIONS........................................................................................................ 30

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Figure Index
FIGURE 1: BC68&M66 PIN ASSIGNMENT...................................................................................................... 10
FIGURE 2: REFERENCE CIRCUIT OF POWER SUPPLY .............................................................................. 14
FIGURE 3: REFERENCE CIRCUIT OF VBAT.................................................................................................. 15
FIGURE 4: DRIVING CIRCUIT OF THE PWRKEY........................................................................................... 15
FIGURE 5: TIMING OF POWER-ON SCENARIO ............................................................................................ 16
FIGURE 6: TIMING OF POWER-DOWN THROUGH AT COMMAND.............................................................. 17
FIGURE 7: TIMING OF POWER-DOWN FOR M66 BY PWRKEY................................................................... 17
FIGURE 8: REFERENCE CIRCUIT OF RESET BY USING DRIVING CIRCUIT............................................. 18
FIGURE 9: TIMING OF RESETTING MODULE ............................................................................................... 18
FIGURE 10: REFERENCE CIRCUIT OF NETLIGHT ....................................................................................... 19
FIGURE 11: REFERENCE CIRCUIT OF (U)SIM CARD INTERFACE WITH A 6-PIN (U)SIM CARD
CONNECTOR............................................................................................................................................ 19
FIGURE 12: REFERENCE DESIGN OF M66 UART INTERFACE................................................................... 20
FIGURE 13: REFERENCE DESIGN OF BC68 UART INTERFACE FOR 3.3V SYSTEM................................ 21
FIGURE 14: REFERENCE CIRCUIT OF RF INTERFACE............................................................................... 22
FIGURE 15: BOTTOM VIEW OF BC68/M66 .................................................................................................... 23
FIGURE 16: RECOMMENDED FOOTPRINT OF BC68/M66 (UNIT: MM) ....................................................... 24
FIGURE 17: RECOMMENDED STENCIL DESIGN FOR BC68 (UNIT: MM).................................................... 25
FIGURE 18: RECOMMENDED STENCIL DESIGN FOR M66 (UNIT: MM)...................................................... 26
FIGURE 19: INSTALLATION SKETCH MAP FOR BC68/M66.......................................................................... 27
FIGURE 20: REFLOW SOLDERING THERMAL PROFILE.............................................................................. 28
FIGURE 21: TAPE DIMENSIONS..................................................................................................................... 29
FIGURE 22: REEL DIMENSIONS..................................................................................................................... 29

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BC68&M66 Compatible Design
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1Introduction
Quectel BC68 is a high-performance NB-IoT module compatible with Quectel GSM/GPRS M66 module.
This document briefly describes the compatible design between BC68 and M66 modules.

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BC68&M66 Compatible Design
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2General Descriptions
2.1. Product Description
M66 is a Quad-band GSM/GPRS engine that works at frequencies of GSM850MHz, EGSM900MHz,
DCS1800MHz and PCS1900MHz. The M66 features GPRS multi-slot class 12 and supports the GPRS
coding schemes CS-1, CS-2, CS-3 and CS-4. BC68 is a high-performance NB-IoT module with low
power consumption. BC68 and M66 are designed as compatible products. Customers can choose a
proper module according to specific application demands. The compatible design guideline ensures a
smooth migration from M66 to BC68 for customers’ products.
Table 1: Module General Information
Module
Appearance
Packaging
Dimensions
Description
BC68
44-pin LCC
14-pin LGA
17.7mm ×15.8mm ×2.0mm
NB-IoT module
M66
44-pin LCC
17.7mm ×15.8mm ×2.3mm
GSM/GPRS
module

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BC68&M66 Compatible Design
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2.2. Features Overview
The following table compares general properties and features of BC68 and M66 modules.
Table 2: Features Overview
Feature
BC68
M66
Power Supply
3.1V~4.2V
Typ. 3.6V
3.3V~4.6V
Typ. 4.0V
Peak Current
VBAT: Max 0.8A
VBAT: Max 0.8A
Sleep Current
Max 5uA @Power Saving Mode
(PSM)
1.3mA @DRX=5
1.2mA @DRX=9
Frequency Bands
H-FDD:
B1/B3/B5/B8/B20/B28*
Quad-band:
GSM850MHz/EGSM900MHz/
DCS1800MHz/PCS1900MHz
GSM
Not supported
Supported
NB-IoT
Supported
Not supported
GPRS
Not supported
Multi-slot class 12
BT
Not supported
Supported BT3.0
Temperature Range
Operation temperature range:
-35°C ~ +75°C 1)
Extended temperature range:
-40°C ~ +85°C 2)
Storage temperature range:
-40°C ~ +90°C
Operation temperature range:
-35°C ~ +75°C 1)
Extended temperature range:
-40°C ~ +85°C 2)
Storage temperature range:
-40°C ~ +90°C
UART Interface
Main port:
When used forAT command
communication and data
transmission, the baud rate is
4800bps, 9600bps (default) and
115200bps
When used for firmware upgrading,
the baud rate is 921600bps
Debug port:
Used for firmware debugging
Only supports 921600bps baud rate
Signal level: 3.0V
Baudrate:
300bps to 115200bps
Autobauding:
4800bps to 115200bps
Flow control: RTS/CTS
Signal level: 2.8V
Analog Audio
Not supported
One analog input channel

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BC68&M66 Compatible Design
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1. 1) Within operation temperature range, the module is 3GPP compliant.
2. 2) Within extended temperature range, the module remains the ability to establish and maintain a
voice, SMS, data transmission, emergency call, etc. There is no unrecoverable malfunction. There
are also no effects on radio spectrum and no harm to radio network. Only one or more parameters like
Pout might reduce in their value and exceed the specified tolerances. When the temperature returns to
normal operating temperature levels, the module will meet 3GPP specifications again.
3. “*” means under development.
Two analog output channels
ADC
ADC*
Supported
RTC Backup
Not supported
Vnorm=2.8V
VI=1.5V~3.3V
PCM Interface
Not supported
Supported
Firmware Upgrade
UART, DFOTA
UART
NOTES

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BC68&M66 Compatible Design
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2.3. Pin Assignment
The following figure shows the pin assignment of BC68 and M66.
GND
RESERVED
RESERVED
SIM_RST
SIM_CLK
RESERVED
VBAT
GND
GND
DBG_TXD
RESERVED
GND
GND
RF_ANT
14 15 16 17 18 19 20 21 22 36
37 38 39 40 41 42 43 44
1
2
3
4
5
6
7
8
9
10
11
12
13 23
24
25
26
27
28
29
30
31
32
33
34
35
RESERVED
ADC*
SIM_GND
SIM_DATA
GND
GND
RESERVED
RESERVED
VDD_EXT
RI
TXD
RXD
NETLIGHT*
RESET
SIM_VDD
VBAT
BC68
M66
+
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED RESERVED RESERVED
RESERVED
RESERVED
RESERVED
45
46
47
48
49 50 51
52
53
54
55
56
57
58
BC68/M66
Top View
AGND
SPK2P
MICP
MICN
SPK1P
SPK1N
PWRKEY
AVDD
ADC0
SIM_GND
SIM_DATA
SIM_VDD
RESERVED
RI
TXD
RXD
NETLIGHT
DTR
DCD
CTS
SIM_RST
SIM_CLK
RF_ANT
GND
GND
BT_ANT
RFTXMON
VDD_EXT
PCM_OUT
PCM_IN
PCM_SYNC
PCM_CLK
RTS
TXD_AUX
RXD_AUX
VRTC
VBAT
GND
GND
DBG_TXD
DBG_RXD
GND
GND
VBAT
Figure 1: BC68&M66 Pin Assignment
1. The black colored pin names are defined for BC68 module.
2. The green colored pin names are defined for M66 module.
3. The orange colored pins of BC68 are additional pins compared with M66.
NOTES

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BC68&M66 Compatible Design
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3Pin Description
This chapter describes the pin definition of BC68 and M66, as well as the pin comparison between them.
Table 3: I/O Parameters Definition
The following table shows the comparison of pins between BC68 and M66.
Table 4: Pin Comparison between BC68 and M66
Symbol
Description
IO
Bidirectional
DI
Digital Input
DO
Digital Output
PI
Power Input
PO
Power Output
AI
Analog Input
AO
Analog Output
OD
Open Drain
Pin No.
BC68
M66
Pin Name
IO
Description
Pin Name
IO
Description
1
GND
AGND
Analog ground. Separate
ground connection for
external audio circuits
2
RESERVED
/
/
SPK2P
AO
Channel 2 voice output
3
RESERVED
/
/
MICP
AI
Positive voice input
4
RESERVED
/
/
MICN
AI
Negative voice input
signal

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5
RESERVED
/
/
SPK1P
AO
Channel 1
Positive voice output
6
RESERVED
/
/
SPK1N
AO
Channel 1
Negative voice output
7
RESERVED
/
/
PWRKEY
DI
Used to power on/off the
module
8
RESERVED
/
/
AVDD
PO
Reference voltage of
ADC circuit
9
ADC*
AI
General purpose
analog to digital
converter
ADC0
AI
General purpose analog
to digital converter
10
SIM_GND
USIM ground
SIM_GND
Specified ground for
USIM card
11
SIM_DATA
IO
USIM data
SIM_DATA
IO
(U)SIM card data signal
12
SIM_RST
DO
USIM reset
SIM_RST
DO
(U)SIM card reset signal
13
SIM_CLK
DO
USIM clock
SIM_CLK
DO
(U)SIM card clock signal
14
SIM_VDD
PO
Power supply for
USIM card
SIM_VDD
PO
Power supply for (U)SIM
card
15
RESET
DI
Reset the module
RESERVED
/
/
16
NETLIGHT*
DO
Network status
indication
NETLIGHT
DO
Network status indication
17
TXD
DO
Transmit data
TXD
DO
Transmit data
18
RXD
DI
Receive data
RXD
DI
Receive data
19
DTR
DI
Data terminal
ready
DTR
DI
Data terminal ready
20
RI
DO
Ring indication
RI
DO
Ring indication
21
RESERVED
/
/
DCD
DO
Data carrier detection
22
RESERVED
/
/
CTS
DO
Clear to send
23
RESERVED
/
/
RTS
DI
Request to send
24
VDD_EXT
PO
3.0V output power
supply for external
circuits.
It cannot be used
to supply power for
external circuits
when in PSM.
VDD_EXT
PO
Supply 2.8V voltage for an
external circuit.

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BC68&M66 Compatible Design
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1. The red colored pins are compatible pins with different functionalities.
2. The black colored pins are compatible pins with the same functionality.
3. The orange colored pins of BC68 are additional pins compared with M66.
4. Keep all reserved and unused pins unconnected.
5. All GND pins should be connected to ground.
6. “*” means under development.
25
RESERVED
/
/
RFTXMON
DO
Transmission signal
indication
26
RESERVED
/
/
BT_ANT
IO
BT antenna pad
28
RESERVED
/
/
RXD_AUX
DI
Receive data
29
RESERVED
/
/
TXD_AUX
DO
Transmit data
30
RESERVED
/
/
PCM_CLK
DO
PCM clock
31
RESERVED
/
/
PCM_SYNC
DO
PCM frame
synchronization
32
RESERVED
/
/
PCM_IN
DI
PCM data input
33
RESERVED
/
/
PCM_OUT
DO
PCM data output
35
RF_ANT
IO
RF antenna pad
RF_ANT
IO
RF antenna pad
38
RESERVED
/
/
DBG_RXD
DI
Receive data
39
DBG_TXD
DO
Transmit data
DBG_TXD
DO
Transmit data
42
VBAT
PI
Main power supply
of the module:
VBAT=3.1V~4.2V
VBAT
PI
Main power supply of
module:
VBAT=3.3V~4.6V
43
VBAT
PI
Main power supply
of the module:
VBAT=3.1V~4.2V
VBAT
PI
Main power supply of
module:
VBAT=3.3V~4.6V
44
RESERVED
/
/
VRTC
IO
Power supply for RTC
when VBAT is not
supplied for the module.
27, 34,
36, 37,
40, 41,
GND
/
Ground
GND
/
Ground
45~58
RESERVED
/
/
/
/
/
NOTES

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BC68&M66 Compatible Design
BC68&M66_Compatible_Design 14 / 31
4Hardware Reference Design
The following chapters describe the compatible design between BC68 and M66 on main functionalities.
4.1. Power Supply
4.1.1. Reference Design for Power Supply
The power design for the module is very important, as the performance of a module largely depends on
the power source. The power supply for BC68 and M66 should be able to provide sufficient current up to
2A.
A TVS diode needs to be added on the VBAT trace to increase surge voltage withstand capability. The
following figure shows a reference design for battery power supply and the designed output of the power
supply is about 3.6V.
Battery
OUTGND
VBAT
C1
470uF
C2
1uF
TVS
Figure 2: Reference Circuit of Power Supply
4.1.2. Reduce Voltage Drop
The power supply range of BC68 is from 3.1V to 4.2V. The power supply range of M66 is 3.3V to 4.6V
Attention should be paid to the range of the power source to make sure that the input voltage will never
drop below 3.3V and never exceed 4.2V. In addition, in order to get a stable output voltage, a TVS diode
also needs to be added on the VBAT trace to increase surge voltage withstand capability.

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BC68&M66 Compatible Design
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BC68/M66 Module
VBAT
C1
100uF
+C2
100nF
C3
33pF
C4
10pF
D1
VBAT
Figure 3: Reference Circuit of VBAT
4.2. Power-on Circuit
The turn-on method of BC68 is different from M66. BC68 can be powered on automatically when VBAT
pins are powered. M66 will be powered on by driving the pin PWRKEY to a low level voltage for more than
100ms, and an open collector driver circuit is suggested to control the PWRKEY. The following is a
reference design for power-on circuit of M66.
Turn on pulse
PWRKEY
4.7K
47K
≥100ms
Figure 4: Driving Circuit of the PWRKEY

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The power-on scenario of BC68 and M66 are illustrated in the figure below.
VDD_EXT
(OUTPUT)
VIL<0.1*VBAT
VIH > 0.6*VBAT
VBAT
PWRKEY
(INPUT) 54ms
>1s
T1
OFF BOOTING
M66 RUNNING
BC68 BOOTING
Figure 5: Timing of Power-on Scenario
1. Please make sure VBAT is stable before pulling down PWRKEY pin. The time of T1is recommended
to be 100ms. It is not recommended to always pull down PWRKEY pin.
2. The parts marked in green in the above figure are for BC68.
3. The parts marked in black in the above figure are for M66.
4.3. Power-off Circuit
4.3.1. Power down Module via AT Command
M66 can be turned off through AT+QPOWD command. It is a safe way to turn off the module. This
command will let the module log out from the network and allow the firmware to save important data
before completely disconnecting the power supply. For more details about the command, please refer to
document [1].
BC68 can be turned off by shutting down the VBAT power supply.
The power-down scenario is illustrated in the figure below.
NOTES

GSM/GPRS/NB-IoT Module Series
BC68&M66 Compatible Design
BC68&M66_Compatible_Design 17 / 31
STATUS
VBAT
AT+QPOWD
Log out from the network in 2s~40s
RUNNING Power-down procedure OFF
M66
RXD M66
RUNNING
BC68 OFF
Figure 6: Timing of Power-down through AT Command
1. The parts marked in green in the above figure are for BC68.
2. The parts marked in black in the above figure are for M66.
3. The time for the module to log out from network depends on local network quality.
4.3.2. Power down M66 Using PWRKEY Pin
It is a safe way to turn off M66 module by driving PWRKEY to a low level voltage for 0.7s~1s, while BC68
could not be turned off by this pin.
The power-down scenario for M66 by PWRKEY is illustrated in the figure below.
VBAT
PWRKEY
(INPUT)
VDD_EXT
(OUTPUT)
Log out from the network in 2s~12s
0.7s<Pulldown<1s
Figure 7: Timing of Power-down for M66 by PWRKEY
NOTES

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BC68&M66_Compatible_Design 18 / 31
4.4. Reset BC68
The BC68 can be reset by the following two ways:
Hardware
The module can be reset by driving RESET to a low level voltage for more than 100ms. The reset
scenario for BC68 by RESET is illustrated in the figure below.
4.7K
47K
pulse
BC68
RESET
>100ms
>100ms
Figure 8: Reference Circuit of RESET by Using Driving Circuit
The reset scenario is illustrated in the figure below.
VBAT
RESET
≥100ms
RUNNING OFF RUNNING
≥1.4s
BC68
Figure 9: Timing of Resetting Module
Software
Reset the module using command AT+NRB. For more details about the command, please refer to
document [2].

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BC68&M66_Compatible_Design 19 / 31
4.5. Network Status Indication
The NETLIGHT pin can be used to drive a network status indicator LED. A reference design is shown
below.
4.7K
47K
VBAT
2.2K
BC68/M66 Module
NETLIGHT
Figure 10: Reference Circuit of NETLIGHT
4.6. (U)SIM Interface
M66 supports 1.8V or 3.0V SIM/USIM cards, while BC68 supports 1.8V or 3.0V USIM cards. The pin
assignment of BC68’s USIM interface and M66’s (U)SIM interface is compatible.
The following figure shows a reference design for (U)SIM interface with a 6-pin (U)SIM card connector.
22R
22R
22R
100nF (U)SIM Card Connector
GND
ESD
33pF 33pF 33pF
VCC
RST
CLK IO
VPP
GND
GND
15K
SIM_VDD
SIM_GND
BC68/M66 Module
SIM_VDD
SIM_RST
SIM_CLK
SIM_DATA
Figure 11: Reference Circuit of (U)SIM Card Interface with a 6-Pin (U)SIM Card Connector