L76 Hardware Design
GNSS Module Series
Rev. L76_Hardware_Design_V1.1
Date: 2013-02-25
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About the document
History
Revision
Date
Author
Description
V1.0
2013-02-08
Ray XU
Initial
V1.1
2013-03-21
Ray XU
1. Delete PMTK 291 command.
2. Changed R3 to 100R in Figure 17.
3. Updated chapter 2.4.
4. Changed typical voltage of V_BCKP
to 3.3V.
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Contents
About the document ................................................................................................................................... 2
Contents ....................................................................................................................................................... 3
Table Index ................................................................................................................................................... 5
Figure Index ................................................................................................................................................. 6
1 Introduction .......................................................................................................................................... 7
2 Product Concept .................................................................................................................................. 8
2.1. General Description................................................................................................................... 8
2.2. Key Features ............................................................................................................................. 9
2.3. Block Diagram ......................................................................................................................... 10
2.4. Evaluation Board ..................................................................................................................... 10
2.5. The Module Supports Protocols .............................................................................................. 11
3 Application .......................................................................................................................................... 12
3.1. Pin Assignment ........................................................................................................................ 12
3.2. Pin Definition ........................................................................................................................... 12
3.3. Power Supply .......................................................................................................................... 14
3.4. Operate Mode ......................................................................................................................... 16
3.4.1. Full On Mode .................................................................................................................. 16
3.4.2. Standby Mode ................................................................................................................ 17
3.4.3. Backup Mode ................................................................................................................. 18
3.4.4. Period Mode ................................................................................................................... 20
3.4.5. AlwaysLocateTM Mode ................................................................................................... 22
3.5. RESET ..................................................................................................................................... 23
3.6. UART Interface ........................................................................................................................ 24
3.7. EASY Technology .................................................................................................................... 26
3.8. Multi-tone AIC .......................................................................................................................... 26
3.9. ANTON .................................................................................................................................... 27
3.10. LOCUS .................................................................................................................................... 27
4 Antenna Interface ............................................................................................................................... 28
4.1. Antenna Specification ............................................................................................................. 28
4.2. Recommended Circuit for Antenna ......................................................................................... 29
4.2.1. Active Antenna ............................................................................................................... 29
4.2.2. Passive Antenna ............................................................................................................ 31
5 Electrical, Reliability and Radio Characteristics ............................................................................ 33
5.1. Absolute Maximum Ratings .................................................................................................... 33
5.2. Operating Conditions .............................................................................................................. 34
5.3. Current Consumption .............................................................................................................. 34
5.4. Electro-static Discharge .......................................................................................................... 35
5.5. Reliability Test ......................................................................................................................... 36
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6 Mechanics ........................................................................................................................................... 37
6.1. Mechanical View Of The Module ............................................................................................ 37
6.2. Bottom Dimension and Recommended Footprint ................................................................... 38
6.3. Top View Of The Module ......................................................................................................... 39
6.4. Bottom View of the Module ..................................................................................................... 39
7 Manufacturing .................................................................................................................................... 40
7.1. Assembly and Soldering ......................................................................................................... 40
7.2. Moisture Sensitivity ................................................................................................................. 41
7.3. ESD Safe ................................................................................................................................. 41
7.4. Tape and Reel ......................................................................................................................... 41
7.5. Ordering Information ............................................................................................................... 42
8 Appendix Reference .......................................................................................................................... 43
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Table Index
TABLE 1: FEATURE ............................................................................................................................................ 9
TABLE 2: THE PROTOCOL SUPPORTED BY THE MODULE ......................................................................... 11
TABLE 3: PIN DESCRIPTION ........................................................................................................................... 12
TABLE 4: MODULE STATE SWITCH ................................................................................................................ 16
TABLE 5: DEFAULT CONFIGURATION ............................................................................................................ 17
TABLE 6: PMTK COMMAND FORMAT ............................................................................................................ 20
TABLE 7: RECOMMENDED ANTENNA SPECIFICATION ............................................................................... 28
TABLE 8: ABSOLUTE MAXIMUM RATINGS .................................................................................................... 33
TABLE 9: THE MODULE POWER SUPPLY RATINGS..................................................................................... 34
TABLE 10: THE MODULE CURRENT CONSUMPTION .................................................................................. 34
TABLE 11: THE ESD ENDURANCE TABLE (TEMPERATURE: 25℃, HUMIDITY: 45 %) ............................... 35
TABLE 12: RELIABILITY TEST ......................................................................................................................... 36
TABLE 13: TRAY PACKING .............................................................................................................................. 42
TABLE 14: ORDERING INFORMATION ........................................................................................................... 42
TABLE 15: RELATED DOCUMENTS ................................................................................................................ 43
TABLE 16: TERMS AND ABBREVIATIONS ...................................................................................................... 43
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Figure Index
FIGURE 1: BLOCK DIAGRAM .......................................................................................................................... 10
FIGURE 2: PIN ASSIGNMENT ......................................................................................................................... 12
FIGURE 3: INTERNAL POWER CONSTRUCTION .......................................................................................... 15
FIGURE 4: CURRENT AND CONSUMPTION VERSUS VCC ......................................................................... 15
FIGURE 5: RTC SUPPLY FROM NON-CHARGEABLE BATTERY .................................................................. 19
FIGURE 6: REFERENCE CHARGING CIRCUIT FOR CHARGEABLE BATTERY .......................................... 19
FIGURE 7: SEIKO MS920SE CHARGE AND DISCHARGE CHARACTERISTICS ......................................... 20
FIGURE 8: PERIOD TIMING ............................................................................................................................. 22
FIGURE 9: ALWAYSLOCATETM MODE ............................................................................................................ 23
FIGURE 10: REFERENCE RESET CIRCUIT USING OC CIRCUIT ................................................................. 24
FIGURE 11: MODULE TIMING ......................................................................................................................... 24
FIGURE 12: CONNECTION OF SERIAL INTERFACES .................................................................................. 25
FIGURE 13: RS-232 LEVEL SHIFT CIRCUIT ................................................................................................... 25
FIGURE 14: REFERENCE DESIGN WITH ACTIVE ANTENNA ....................................................................... 29
FIGURE 15: REFERENCE DESIGN FOR ACTIVE ANTENNA WITH ANTON ................................................. 30
FIGURE 16: REFERENCE DESIGN WITH PASSIVE ANTENNA .................................................................... 31
FIGURE 17: REFERENCE DESIGN FOR PASSIVE ANTENNA WITH LNA .................................................... 32
FIGURE 18: TOP VIEW AND SIDE VIEW（UNIT: MM） ................................................................................. 37
FIGURE 19: BOTTOM DIMENSION（UNIT: MM） .......................................................................................... 38
FIGURE 20: FOOTPRINT OF RECOMMENDATION（UNIT: MM） ................................................................ 38
FIGURE 21: TOP VIEW OF THE MODULE ...................................................................................................... 39
FIGURE 22: BOTTOM VIEW OF THE MODULE .............................................................................................. 39
FIGURE 23: RAMP-SOAK-SPIKE-REFLOW OF FURNACE TEMPERATURE ............................................... 40
FIGURE 24: TAPE AND REEL SPECIFICATION .............................................................................................. 41
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1 Introduction
This document defines and specifies L76 GNSS module. It describes L76 GNSS module hardware
interface and its external application reference circuits, mechanical size and air interface.
This document can help you quickly understand the interface specifications, electrical and mechanical
details of L76 GNSS module. We also offer you other documents such as L76 software application notes
and user guider. These documents can ensure you use L76 module to design and set up mobile
applications quickly.
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2 Product Concept
2.1. General Description
L76 is a single receiver module integrated with GLONASS and GPS system. It is able to achieve the
industry’s highest level of sensitivity, accuracy and TTFF with the lowest power consumption in a
small-footprint lead-free package. The embedded flash memory provides capacity for storing
user-specific configurations and allows for future updates.
The L76 GNSS module supports multiple positions and navigation system including autonomous GPS,
GLONASS, SBAS (including WAAS, EGNOS, MSAS and GAGAN), QZSS, and AGPS.
Embedded with many advanced power saving modes including period, AlwaysLocateTM, standby and
backup, L76 GNSS module has excellent low-power consumption in different scenes.
EASY technology as the key feature of L76 is one kind of AGPS. Collecting and processing all internal
aiding information like GPS time, Ephemeris, Last Position etc, the GNSS module will have a fast TTFF in
either Hot or Warm start.
L76 GNSS module is an SMD type module with the compact 10.1mm x 9.7mm x 2.5mm form factor,
which can be embedded in your applications through the 18-pin pads. It provides necessary hardware
interfaces between the module and your board.
The module is fully ROHS compliant to EU regulation.
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2.2. Key Features
Table 1: Feature
Feature
Implementation
GNSS
GPS&GLONASS
Power supply
Supply Voltage: 2.8V – 4.3V typical : 3.3V
Power consumption
Acquisition 21 mA @ -130dBm(GPS)
Tracking 15 mA @ -130dBm(GPS)
Acquisition 25 mA @ -130dBm(GPS+GLONASS)
Tracking 18 mA @ -130dBm(GPS+GLONASS)
Receiver Type
GPS L1 1575.42MHz C/A Code
GLONASS L1 1598.0625~1605.375 C/A Code
Sensitivity(NOTE)
Acquisition -148dBm
Reacquisition -160dBm
Tracking -163dBm
Time-To-First-Fix
(EASY enabled)
Cold Start <15s average@-130dBm
Warm Start <5s average@-130dBm
Hot Start 1s @-130dBm
Time-To-First-Fix
(EASY disabled)
Cold Start (Autonomous) <35s average@-130dBm
Warm Start (Autonomous) <30s average@-130dBm
Hot Start (Autonomous) 1s@-130dBm
Horizontal Position
Accuracy(autonomous)
<2.5 m CEP@-130dBm
Update Rate
Up to 10Hz,1Hz by default
Accuracy of 1PPS Signal
Typical accuracy <15ns (Not support time service)
Time pulse width 100ms
Velocity Accuracy
Without Aid 0.1m/s
Acceleration Accuracy
Without Aid 0.1m/s²
Dynamic Performance
Maximum Altitude 18,000m
Maximum Velocity 515m/s Maximum
Acceleration 4G
UART Port
UART Port: TXD1 and RXD1
Supports baud rate from 4800bps to 115200bps,9600bps by default
UART Port is used for NMEA output, MTK proprietary messages input
and firmware upgrade
Temperature range
Normal operation: -45°C ~ +85°C
Storage temperature: -45°C ~ +125°C
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2.3. Block Diagram
The following figure shows a block diagram of L76 GNSS module. It consists of a single chip GNSS IC
which includes RF part and Baseband part, a SAW filter, a TCXO and a crystal oscillator.
Flash
RF F
r
on
t
-
E
nd
In
t
e
g
r
a
t
e
d
L
NA
Fractional-N
Syntheszer
GNSS
Engine
ROM
Saw
filter PMU
ARM7
Processor
Peripheral
controller
RTC
RAM
RF_IN
Active
Interference
Cancellation
TCXO
32.768K XTAL
VCC
V_BCKP
UART
RESET
STANDBY
1PPS
VCC_RF
ANTON
FORCE_ON
Figure 1: Block Diagram
2.4. Evaluation Board
In order to help you use L76 GNSS module on your applications, Quectel supplies an Evaluation Board
(EVB) with Micro-USB cable, active antenna and other peripherals to test the module.
For more details, please refer to the document [1].
Physical Characteristics
Size: 10.1±0.15 x 9.7±0.15 x 2.5±0.15mm
Weight: Approx. 0.6g
NOTE
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2.5. The Module Supports Protocols
Table 2: The Protocol Supported by the Module
Protocol
Type
NMEA
Input/output, ASCII, 0183, 3.01
PMTK
Input, MTK proprietary protocol
NOTE
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3 Application
The module is equipped with an 18-pin 1.1mm pitch SMT pad that connects to your application platform.
Sub-interfaces included in these pads are described in details in the following chapters.
3.1. Pin Assignment
2
3
4
5
7
8
RXD1
1
TXD1
9
6
17
16
15
14
12
11
18
10
13 V_BCKP
NC
VCC
RESET
GND
RF_IN
GND
VCC_RF
ANTON
NC
FORCE_ON
STANDBY
1PPS
(Top View)
L76
RESERVED
RESERVED
GND
Figure 2: Pin Assignment
3.2. Pin Definition
Table 3: Pin Description
Power Supply
Pin Name
Pin No.
I/O
Description
DC Characteristics
Comment
VCC
8
I
Main power
supply
Vmax= 4.3V
Vmin=2.8V
Vnom=3.3V
Assure load current no
less than 150mA.
V_BCKP
6
I
Backup power
supply
Vmax=4.5V
Vmin=1.5V
Supply power for RTC
domain when VCC is
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Vnom=3.3V
IV_BCKP=7uA@Backup
mode
powered off.
VCC_RF
14
O
Supply Power for
external RF
component
Vmax=4.3V
Vmin=2.8V
Vnom=3.3V
Usually supply power for
external active antenna or
LNA. If unused, keep this
pin open. VCC_RF ≈
VCC
Reset
Pin Name
Pin No.
I/O
Description
DC Characteristics
Comment
RESET
9
I
System reset
VILmin=-0.3V
VILmax=0.7V
VIHmin=2.1V
VIHmax= 3.1V
It is low level active.
If unused, keep this pin
open or connect it to VCC.
UART port
Pin Name
Pin No.
I/O
Description
DC Characteristics
Comment
RXD1
3
I
Receive data
VILmin=-0.3V
VILmax=0.7V
VIHmin=2.1V
VIHmax= 3.1V
TXD1
2
O
Transmit data
VOLmax=0.42V
VOHmin=2.4V
VOHnom=2.8V
RF interface
Pin Name
Pin No.
I/O
Description
DC Characteristics
Comment
RF_IN
11
I
RF signal input
Characteristic
impedance of 50Ω
Refer to chapter 4
Other interface
Pin Name
Pin No.
I/O
Description
DC Characteristics
Comment
ANTON
13
O
External LNA
control pin and
active antenna
power control pin
in power save
mode
VOLmax=0.42V
VOHmin=2.4V
VOHnom=2.8V
If unused, keep this pin
open.
STANDBY
5
I
Used to enter
into or exit from
standby mode
VILmin=-0.3V
VILmax=0.7V
VIHmin=2.1V
It is pulled up internally.
It is edge-triggered.
If unused, keep this pin
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VIHmax= 3.1V
open.
1PPS
4
O
One pulse per
second
VOLmax=0.42V
VOHmin=2.4V
VOHnom=2.8V
Synchronized at rising
edge, the pulse width
is100ms. If unused, keep
this pin open.
FORCE_
ON
18
I
Logic high will
force module to
be waked up
from backup
mode
VILmin=-0.3V
VILmax=0.7V
VIHmin=2.1V
VIHmax= 3.1V
Keep this pin open or
pulled low before entering
into backup mode.
It belongs to RTC domain.
If unused, keep this pin
open.
RESERV-
ED
16,17
Keep these pins open.
3.3. Power Supply
VCC pin supplies power for BB, RF, I/O and RTC domain. The load current of VCC pin varies according
to the VCC level, processor load and satellite acquisition. Typical VCC peak current is 40 mA (typ.) during
GPS acquisition after power up. So it is important to supply sufficient current and make the power clean
and stable. VCC supply ripple voltage should meet the requirement: 54 mV (RMS) max @ f = 0… 3MHz
and 15 mV (RMS) max @ f > 3 MHz. You should choose the LDO without built-in output high-speed
discharge function to keep long output voltage drop-down period. The decouple combination of 10uF and
100nF capacitor is recommended nearby VCC pin.
The V_BCKP pin supplies power for RTC domain. A cell battery with the combination of 4.7uF and 100nF
capacitor is recommended nearby V_BCKP pin. The voltage of RTC domain ranges from 1.5V to 4.5V. In
order to achieve a better Time To First Fix (TTFF), RTC domain should be valid all the time. It can supply
power for SRAM memory in RTC domain which contains all the necessary GPS information for quick
start-up and a small amount of user configuration variables.
The module’s internal power construction is shown as below.
VCC pin not only supplies power for PMU but also for VCC_RF and RTC domain. V_BCKP supplies
power for RTC domain only. The two diode in following figure construct an OR gate supply power for RTC
domain. FORCE_ON pin belongs to RTC domain. The signal which has been shown as red line in the
following diagram can open and close the switch. The following action will close and open the switch:
The switch will be closed by default when VCC is supplied power (VCC off on).
Based on above step, FORCE_ON open or low and sending PMTK command can open the switch
(full on backup).
Based on above step, FORCE_ON logic high can close the switch (backup full on).
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PMU VCC
V_BCKP
VCC_RF
FORCE_ON
RTC
ARM
Logic
circuit
RTC
power
Figure 3: Internal Power Construction
The following picture shows average current and power consumption versus VCC supply voltage. It was
tested in the open sky and tracking mode based on GPS&GLONASS.
Figure 4: Current and Consumption Versus VCC
0
10
20
30
40
50
60
70
4.3
4.1
3.9
3.7
3.5
3.3
3.1
2.8
Current(mA)
Power(mW)
NOTE
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3.4. Operate Mode
The table below briefly illustrates the relationship among different operating modes of L76 GNSS module
Table 4: Module State Switch
Current
Mode
Next Mode
Backup
Standby
Full on
Period
Always Locate
Backup
N/A
N/A
Refer to chapter 3.4.3
N/A
N/A
Standby
N/A
N/A
Pull STANDBY high
Send any data via
UART1
N/A
N/A
Full on
Refer to
chapter 3.4.3
Pull STANDBY low
PMTK161
N/A
PMTK
225
PMTK225
Period
N/A
N/A
Refer to chapter 3.4.4
N/A
N/A
Always
locate
N/A
N/A
Refer to chapter 3.4.5
N/A
N/A
3.4.1. Full On Mode
Full on mode includes tracking mode and acquisition mode. Acquisition mode is defined as the module
starts to search satellites, determine visible satellites and coarse carrier frequency and code phase of
satellite signals. When the acquisition is completed, it switches to tracking mode automatically. Tracking
mode is defined as the module tracks satellites and demodulates the navigation data from the specific
satellites.
Whether the combination of VCC and V_BCKP pins is valid or VCC is valid, the module will enter into full
on mode automatically and follow the default configuration as below. You can refer to chapter 3.3 about
internal power construction to have a good comprehension. You also can use PMTK commands to
change the configuration to satisfy the requirement.
NOTE
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Table 5: Default Configuration
Item
Configuration
Comment
Baud rate
9600bps
Protocol
NMEA
RMC, VTG, GGA, GSA, GSV and GLL
Update rate
1Hz
SBAS
Enable
AIC
Enable
LOCUS
Disable
EASY technology
Enable
GNSS
GPS+GLONASS
In full on mode, the consumption will comply with the following regulation:
When the module is powered on, the average current will rush to 40mA and it will last a few seconds, then
the consumption will be decreased to acquisition current marked in table 1 and we defined this state as
acquisition state, also it will last several minutes until it switches to tracking state automatically. The
consumption in tracking state is less than acquisition. The value is also listed in table 1.
Using PMTK commands can switch among multiple position system:
$PMTK353,0,1*36: search GLONASS satellites only
$PMTK353,1,0*36: search GPS satellites only
$PMTK353,1,1*37: search GLONASS and GPS satellites
3.4.2. Standby Mode
Standby mode is a low-power consumption mode. In standby mode, the internal core and I/O power
domain are still active, but RF and TCXO are powered off, the module stops satellites search and
navigation. UART1 is still accessible like PMTK commands or any other data, but there is no NEMA
messages output.
There are two ways to enter into standby mode and exit from standby mode.
Using STANDBY pin: Pulling STANDBY low will make the GNSS module to enter into standby
mode and releasing STANDBY which has been pulled high internally will make the module back to
full on mode. Note that pulling down STANDBY pin to ground will cause the extra current
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consumption which makes the typical standby current reach to about 600uA @ VCC=3.3V.
Using PMTK command: Sending PMTK command “$PMTK161,0*28” will enter into standby mode.
Sending any data via UART1 will make the module exiting from standby mode as UART1 is still
accessible in standby mode. When the module exit from standby mode, it will use all internal aiding
information like GPS time, Ephemeris, Last Position etc, resulting to a fastest possible TTFF in either
Hot or Warm start. The typical current consumption in this way is about 500uA @VCC=3.3V in
standby mode.
3.4.3. Backup Mode
Back up mode is a lower power consumption mode than standby mode. In this mode, the module stops to
acquire and track satellites. UART1 is not accessible. But the backed-up memory in RTC domain which
contains all the necessary GPS information for quick start-up and a small amount of user configuration
variables is alive. Due to the backed-up memory, EASY technology is available. The type consumption in
this mode is about 7uA.
There are two ways to enter into backup mode and back to full on mode.
Send command: “$PMTK225,4*2F” (the red line open the switch in Figure 3) to enter into backup
mode forever. The only way to wake up the module is pulling the FORCE_ON high (the red line
closes the switch in Figure 3).
Cutting off VCC and V_BCKP present will make the module to enter into backup mode from full on
mode. As long as the VCC pin is supplied power, the module will enter into full on mode immediately.
But this method is not recommended.
To have a good comprehension, please refer to chapter 3.3 about internal power construction.
The V_BCKP pin can be directly provided by an external capacitor or battery (rechargeable or
non-chargeable). Please refer to the following figure for RTC backup reference design.
NOTE
NOTE
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RTC LDO
MODULE
V_BCKP
Non-chargeable
Backup Battery
4.7uF 100nF
Figure 5: RTC Supply from Non-chargeable Battery
The V_BCKP pin does not support charging function for rechargeable battery. It is necessary to add a
charging circuit for rechargeable battery.
Charge Circuit
VCC
RTC LDO
1K
MODULE
V_BCKP
Chargeable
Backup Battery
4.7uF 100nF
Figure 6: Reference Charging Circuit for Chargeable Battery
Coin-type Rechargeable Capacitor such as MS920SE from Seiko can be used and Schottky diode such
as RB520S30T1G from ON Semiconductor is recommended to be used here for its low voltage drop.
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Figure 7: Seiko MS920SE Charge and Discharge Characteristics
3.4.4. Period Mode
Period mode is a mode that can control the full on mode and standby/backup mode periodically to reduce
power consumption. It contains Period standby mode and Period backup mode.
The format of the command which enters into period mode is as following:
Table 6: PMTK Command Format
Format:
$PMTK225,<Type>,<Run_time>,<Sleep_time>,<2nd_run_time>,<2nd_sleep_time>*<checksum>
<CR><LF>
Parameter
Format
Description
Type
Decimal
Type=1 for Period Backup Mode
Type=2 for Period Standby Mode
Run_time
Decimal
Run_time = Full on period (ms)
Sleep_time
Decimal
Sleep_time = Standby/Backup period (ms)
2nd_run_time
Decimal
2nd_run_time=Full on period (ms) for extended
acquisition in case module’s acquisition fails during the
Run_time
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2nd_sleep_time
Decimal
2nd_sleep_time = Standby/Backup period (ms) for
extended sleep in case module’s acquisition fails during
the Run_time
Checksum
Hexadecimal
Hexadecimal checksum
Example:
$PMTK225,2,3000,12000,18000,72000*15<CR><LF>
$PMTK225,1,3000,12000,18000,72000*16<CR><LF>
Sending “$PMTK225,0*2B” in any time will make the module to full on mode from Period standby mode
Pulling the FORCE_ON high and sending “$PMTK225,0*2B” immediately will make the module to full on
mode from Period backup mode.
Sending “$PMTK225,0*2B” in Run_time or 2nd_run_time will also make the module to full on mode from
Period backup mode, but it is hard to operate and not recommended.
The following figure has shown the operation of period mode. When you send PMTK command, the
module will be in the full on mode firstly. After several minute, the module will enter into the period mode
and follow the parameters set by you. When the module fails to fix the position in run time, the module
will switch to second run and sleep time automatically. As long as the module fixs the position again, the
module will return to first run and sleep time.
Note that before entering into period mode, assure the module is in the tracking mode; otherwise the
module will have a risk of failure to track the satellite. If GNSS module is located in weak signal
environment, it is better to set the longer second run time to ensure the success of reacquisition.
The average current value can be calculated by the following formula:
I period= (I tracking*T1+Istandby/backup*T2)/ (T1+T2) T1: Run time, T2: Sleep time
Example:
PMTK225,2,3000,12000,18000,72000*15 for period mode with 3s in tracking mode and 12s in standby
mode based on GPS&GLONASS. The average current consumption is calculated below:
I period=(I tracking*T1+Istandby*T2 )/(T1+T2)=(18mA*3s + 0.5mA*12s)/(3s+12s)≈4.0(mA)
NOTES
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PMTK225,1,3000,12000,18000,72000*16 for period mode with 3s in tracking mode and 12s in backup
mode based on GPS&GLONASS. The average current consumption is calculated below:
I period=(I tracking*T1+Ibackup*T2 )/(T1+T2)=(18mA*3s + 0.007mA*12s)/(3s+12s)≈3.6(mA)
Power
Run time Run time
Sleep time Sleep time
Second run timeSecond run time
Second sleep time Second sleep time
Run time Run time
Sleep time Sleep time
Full on
Figure 8: Period Timing
3.4.5. AlwaysLocateTM Mode
AlwaysLocateTM is an intelligent power saving mode. It contains alwaysLocateTM backup mode and
alwaysLocateTM standby mode.
AlwaysLocateTM standby mode supports the module to switch automatically between full on mode and
standby mode. According to the environmental and motion conditions, the module can adaptively adjust
the full on time and standby time to achieve the balance between positioning accuracy and power
consumption. Sending “$PMTK225,8*23” and the module returning: “$PMTK001,225,3*35” means the
module accesses alwaysLocateTM standby mode successfully. It will benefit power saving in this mode.
Sending “$PMTK225,0*2B” in any time will make the module back to full on mode.
AlwaysLocateTM backup mode is the similar with alwaysLocateTM standby mode. The difference is that
AlwaysLocateTM backup mode switches automatically between full on mode and backup mode. The
PMTK command to enter into alwaysLocateTM backup mode is “$PMTK225,9*22”. Pulling FORCE_ON
high and sending “$PMTK225,0*2B” immediately will make the module enter into full on mode.
The position accuracy in AlwaysLocateTM mode will be degraded, especially in high speed. The following
picture shows the rough consumption in different scenes.
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Figure 9: AlwaysLocateTM mode
Example:
The average consumption of the module which is located in outdoor in static and equipped active
antenna after tracking satellites is about 2.7mA in AlwaysLocateTM standby mode based on
GPS&GLONASS.
The average consumption of the module which is located in outdoor in static and equipped active
antenna after tracking satellites is about 2.6mA in AlwaysLocateTM backup mode based on
GPS&GLONASS.
3.5. Reset
L76 GNSS module can be restarted by driving the RESET to a low level voltage for a certain time and
then releasing it. This action will force volatile RAM data loss. Note that Non-Volatile Backup RAM content
is not cleared and thus fast TTFF is possible. An OC driver circuit shown as below is recommended to
control the RESET.
NOTES
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4.7K
47K
RESET
Input pulse
Figure 10: Reference reset circuit using OC circuit
The following picture is shown the timing of L76 module.
VIL<0.8V
VIH >2.0V
Pulldown
> 10ms
RESET
UART Valid ValidInvalidInvalid
VCC
> 2ms
Figure 11: Module timing
3.6. UART Interface
The module provides one universal asynchronous receiver & transmitter serial port. The module is
designed as a DCE (Data Communication Equipment), following the traditional DCE-DTE (Data Terminal
Equipment) connection. The module and the client (DTE) are connected through the following signal
shown as following figure. It supports data baud-rate from 4800bps to 115200bps.
UART port
TXD1: Send data to the RXD signal line of DTE
RXD1: Receive data from the TXD signal line of DTE
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Customer(DTE)
TXD
RXD
GND
Module(DCE)
UART port
TXD1
RXD1
GND
Figure 12: Connection of serial interfaces
This UART port has the following features:
UART port can be used for firmware upgrade, NMEA output and PMTK proprietary messages input.
The default output NMEA type setting is RMC, VTG, GGA, GSA, GSV and GLL.
UART port supports the following data rates:
4800, 9600, 14400, 19200, 38400, 57600, 115200.
The default setting is 9600bps, 8 bits, no parity bit, 1 stop bit.
Hardware flow control and synchronous operation are not supported.
The UART port does not support the RS-232 level but only CMOS level. If the module’s UART port is
connected to the UART port of a computer, it is necessary to add a level shift circuit between the module
and the computer. Please refer to the following figure.
SP3238
3.3V
T5OUT
/SHUTDOWN
V+
GND
V-
VCC
T4OUT
T2OUT
T3OUT
T1OUT
R3IN
R2IN
R1IN
/STATUS
3.3V ONLINE
R1OUT
R2OUT
R3OUT
/R1OUT
T5IN
T4IN
T3IN
T2IN
T1IN
C2+
C2-
C1-
C1+
Module
RXD1
TXD1
9
8
7
6
5
4
3
2
1
15
14
8
9
11
12
5
7
6
10
4
26
2
27
13
18
20
21
16
17
19
22
23
24
3
1
25
28
GND
To PC serial port
Figure 13: RS-232 Level Shift Circuit
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3.7. EASY Technology
Supplying aided information like ephemeris, almanac, rough last position, time, and satellite status，can
help improving GNSS module TTFF and the acquisition sensitivity. We call this EASY technology and The
L76 GNSS module supports it.
EASY technology works as embedded software which can accelerate TTFF by predicting satellite
navigation messages from received ephemeris. The GNSS engine will calculate and predict orbit
information automatically up to 3 days after first receiving the broadcast ephemeris, and saving the
predicted information into the internal memory. GNSS engine will use this information for positioning if no
enough information from satellites, so the function will be helpful for positioning and TTFF improvement.
The EASY function can reduce TTFF to 5s for warm start. In this case, RTC domain should be valid. In
order to gain enough broadcast ephemeris information from GNSS satellites, the GNSS module should
receive the information for at least 5 minutes in the good signal condition after it fix the position.
EASY function is enabled by default. The command “$PMTK869,1,0*34” can be used to disable EASY
function. For more details, please refer to the document [2].
3.8. Multi-tone AIC
L76 GNSS module has a function called multi-tone AIC (Active Interference Cancellation) to decease
harmonic of RF noise from Wi-Fi, Bluetooth, GSM and 3G.
Up to 12 multi-tone AIC embedded in the module can provide effective narrow-band interference and
jamming elimination. The GNSS signal could be demodulated from the jammed signal, which can ensure
better navigation quality. AIC function is enabled by default. Opening AIC function will increase about
1mA @VCC=3.3V consumption. This function is enabled by default. The following commands can be
used to set AIC function.
Enable AIC function: “$PMTK286,1*23”.
Disable AIC function: “$PMTK286,0*22”.
NOTE
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3.9. ANTON
L76 GNSS module provides a pin called ANTON which is related to module state. Its voltage level will
change in different module state. When the module works in full on mode, this pin is high level, while
works in standby mode, backup mode as well as sleep time in period mode and alwaysLocateTM mode,
this pin is low level. Based on this characteristic, this ANTON pin can be used to control the power supply
of active antenna or the enable pin of the external LNA to reduce power consumption. Please refer to
chapter 3.2 for more electrical characteristics about this pin. There is an example of this pin’s application
described in chapter 4.2.
3.10. LOCUS
The L76 GNSS module supports the embedded logger function called LOCUS. It can log position
information to internal flash memory automatically when this function is enabled by sending PMTK
command “$PMTK185,0*22”. Due to this function, the host can go to sleep to save power consumption
and do not need to receive the NMEA information all the time. The module can provide a log capacity of
more than 16 hours.
The detail procedures of this function are as following:
The module has fixed the position (only 3D_fixed is available),
Sending PMTK command “$PMTK184,1*22” to erase internal flash.
Sending PMTK command “$PMTK185,0*22” to start log.
Module logs the basic information (UTC time, latitude, longitude and height) every 15 seconds to
internal flash memory.
Stop logging the information by sending “$PMTK185,1*23”.
MCU can get the data via UART1 by sending “$PMTK622,1*29” to the module.
The raw data which MCU gets has to be parsed via locus parser code provided by Quectel. For more
detail, please contact Quectel FAE department.
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4 Antenna Interface
L76 GNSS module supports both GPS and GLONASS systems. The RF signal is obtained from the
RF_IN pin. The impedance of RF trace should be controlled by 50 Ohm, and the length should be kept as
short as possible.
4.1. Antenna Specification
The L76 GNSS module can be connected to a dedicated GPS/GLONASS passive or active antenna in
order to receive both GPS and GLONASS satellite signals. The recommended antenna specification is
given in following table.
Table 7: Recommended Antenna Specification
Antenna Type
Specification
Passive antenna
GPS frequency: 1575.42±2 MHz
GLONASS frequency : 1602±4 MHz
VSWR: <2 (Typ.)
Polarization: RHCP or Linear
Gain: >0 dBi
Active antenna
GPS frequency: 1575.42±2 MHz
GLONASS frequency : 1602±4 MHz
VSWR: <2 (Typ.)
Polarization: RHCP or Linear
Noise figure: <1.5dB
Gain (antenna): >-2dBi
Gain (embedded LNA): 20dB (Typ.)
Total Gain: >18dBi(Typ.)
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4.2. Recommended Circuit for Antenna
Both active and passive antenna can be used for L76 GNSS module.
4.2.1. Active Antenna
4.2.1.1. Active Antenna without ANTON
The following figure is a typical reference design with active antenna. In this mode, the antenna’s power is
from the VCC_RF.
L76_Module
VCC_RF
Active Antenna
L1 47nH
R2 10R
RF_IN
C1 NM
C2 NM
R1
П matching circuit
0R
Figure 14: Reference Design with Active Antenna
C1, R1, C2 are reserved matching circuit for antenna impedance modification. By default, C1 and C2 are
not mounted, R1 is 0 ohm.
L76 GNSS module provides power supply for external active antenna by VCC_RF. The voltage ranges
from 2.8V to 4.3V, typical value is 3.3V. If the VCC_RF voltage does not meet the requirements for
powering the active antenna, an external LDO should be used.
The inductor L1 is used to prevent the RF signal from leaking into the VCC_RF pin and route the bias
supply to the active antenna and the recommended value of L1 is no less than 47nH. R2 can protect the
whole circuit in case the active antenna is shorted to ground.
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4.2.1.2. Active Antenna with ANTON
L76 GNSS module can also reduce power consumption by controlling the power supply of active antenna
through the pin “ANTON”.
The reference circuit for active antenna with “ANTON” function is given as below.
L76_Module
VCC_RF
ANTON
Active Antenna
L1 47nH R1 R2
10K
Q1
Q2
RF_IN
C1 NM C2 NM
0R
П matching circuit
10R
R3
Power control circuit
Figure 15: Reference Design for Active Antenna with ANTON
ANTON is an optional pin which can be used to control the power supply of the active antenna. When the
ANTON pin is pulled down, MOSFET Q1 and Q2 are in high impedance state and the power supply for
antenna is cut off. When ANTON is pulled high, it will make Q1 and Q2 in the on-state, VCC_RF will
provide power supply for the active antenna. The high and low level of ANTON pin is determined by the
module’s state. Please refer to chapter 3.9 for more detail. If unused, please keep ANTON pin open.
For minimizing the current consumption, the value of resistor R2 should not be too small, and the
recommended value is 10k ohm.
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4.2.2. Passive Antenna
4.2.2.1. Passive Antenna without External LNA
L76_Module
Passive Antenna
RF_IN
C1 NM
C2 NM
R1
П matching circuit
0R
Figure 16: Reference Design with Passive Antenna
The above figure is a typical reference design with passive antenna.
C1, R1, C2 are reserved matching circuit for antenna impedance modification. C1 and C2 are not
mounted by default, R1 is 0 ohm. Impedance of RF trace should be controlled by 50 ohm and the length
should be kept as short as possible.
If an external LNA is added between passive antenna and L76 GNSS module, the total sensitivity will be
improved about 3dB, and the TTFF will be shorter in weak signal, which might be helpful for better
performance.
4.2.2.2. Passive Antenna with External LNA
In order to improve the receiver sensitivity and reduce the TTFF, an external LNA between the passive
antenna and the L76 GNSS module is recommended. The reference design is shown as below.
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L76_Module
VCC_RF
Psssive Antenna
R3
RF_IN
C1 NM
П matching circuit
LNA
RF IN VCC
ENABLE
RF OUT
R1
C2 NM
C3 56pF
100R
ANTON
R2
100R
0R
Figure 17: Reference Design for Passive Antenna with LNA
Here, C1, R1, C2 form a reserved matching circuit for passive antenna and LNA. By default, C1 and C2
are not mounted, R1 is 0 ohm. C3 is reserved for impedance matching between LNA and L76 GNSS
module and the default value of C3 capacitor is 56pF which you might optimize according to the real
conditions. ANTON is an optional pin which can be used to control the enable pin of an external LNA.
NOTES
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5 Electrical, Reliability and Radio
Characteristics
5.1. Absolute Maximum Ratings
Absolute maximum rating for power supply and voltage on digital pins of the module are listed in following
table.
Table 8: Absolute Maximum Ratings
Parameter
Min
Max
Unit
Power supply voltage （VCC）
-0.3
5
V
Backup battery voltage (V_BCKP)
-0.3
5
V
Input voltage at digital pins
-0.3
3.6
V
Input power at RF_IN (PRF_IN)
0
dBm
Storage temperature
-45
125
°C
NOTE
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5.2. Operating Conditions
Table 9: The Module Power Supply Ratings
Parameter
Description
Conditions
Min
Type
Max
Unit
VCC
Supply voltage
Voltage must stay
within the min/max
values, including
voltage drop, ripple,
and spikes.
2.8
3.3
4.3
V
IVCCP
Peak supply current
VCC=3.3V
150
mA
V_BCKP
Backup voltage supply
1.5
3.3
4.5
V
VCC_RF
Output voltage RF
section
VCC
V
TOPR
Full on Operating
temperature
-45
25
85
℃
5.3. Current Consumption
The values for current consumption are shown in following table.
Table 10: The Module Current Consumption
Parameter
Max
Min
Type
Unit
IVCC@Acquisition
@-130dBm(GPS)
21
mA
IVCC @Tracking
@-130dBm (GPS)
15
mA
IVCC@Acquisition
@-130dBm(GPS+GLONASS)
25
mA
IVCC @Tracking
@-130dBm (GPS+GLONASS)
18
mA
NOTES
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5.4. Electro-static Discharge
L76 GNSS module is an ESD sensitive device. ESD protection precautions should still be emphasized.
Proper ESD handing and packaging procedures must be applied throughout the processing, handing and
operation of any application.
The ESD bearing capability of the module is listed in following table. Note that you should add ESD
components to module pins in the particular application.
Table 11: The ESD Endurance Table (Temperature: 25℃, Humidity: 45 %)
Pin
Contact Discharge
Air Discharge
RF_IN
±5KV
±10KV
VCC
±5KV
±10KV
UART
±3KV
±6KV
Others
±2KV
±4KV
IVCC @Standby
@VCC=3.3V
0.5
mA
IBCKP @backup
@V_BCKP=3.3V
7
uA
NOTES
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5.5. Reliability Test
Table 12: Reliability Test
Test item
Condition
Standard
Thermal shock
-30°C...+80°C, 144 cycles
GB/T 2423.22-2002 Test Na
IEC 68-2-14 Na
Damp heat,
cyclic
+55°C; >90% Rh 6 cycles for 144 hours
IEC 68-2-30 Db Test
Vibration shock
5~20Hz,0.96m2/s3;20~500Hz,0.96m2/s3-3dB/oct,
1hour/axis; no function
2423.13-1997 Test Fdb
IEC 68-2-36 Fdb Test
Heat test
85° C, 2 hours, Operational
GB/T 2423.1-2001 Ab
IEC 68-2-1 Test
Cold test
-40° C, 2 hours, Operational
GB/T 2423.1-2001 Ab
IEC 68-2-1 Test
Heat soak
90° C, 72 hours, Non-Operational
GB/T 2423.2-2001 Bb
IEC 68-2-2 Test B
Cold soak
-45° C, 72 hours, Non-Operational
GB/T 2423.1-2001 A
IEC 68-2-1 Test
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6 Mechanics
This chapter describes the mechanical dimensions of the module.
6.1. Mechanical View Of the Module
2.5±0.15
1.0±0.10
9.7±0.15
10.1±0.15
8.84±0.10
9.18±0.10
Figure 18: Top View and Side View（Unit: mm）
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6.2. Bottom Dimension and Recommended Footprint
0.65
9.70
10.10
0.90
0.80 1.10
? 0.50
7.90
0.65
0.650.65
Figure 19: Bottom Dimension（Unit: mm）
0.90 0.90
0.80
1.1
11.50
7.90
0.65
9.70
10.10
Figure 20: Footprint of Recommendation（Unit: mm）
10
18
1
9
NOTE
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6.3. Top View Of The Module
Figure 21: Top View of the Module
6.4. Bottom View of the Module
Figure 22: Bottom View of the Module
9
18
10
1
18
10
9
1
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7 Manufacturing
7.1. Assembly and Soldering
L76 GNSS module is intended for SMT assembly and soldering in a Pb-free reflow process on the top
side of the PCB. It is suggested that the minimum height of solder paste stencil is 130um to ensure
sufficient solder volume. Pad openings of paste mask can be increased to ensure proper soldering and
solder wetting over pads. It is suggested that peak reflow temperature is 235~245ºC (for SnAg3.0Cu0.5
alloy). Absolute max reflow temperature is 260ºC. To avoid damage to the module when it is repeatedly
heated, it is suggested that the module should be mounted after the first panel has been reflowed. The
following picture is the actual diagram which we have operated.
Time(s)
50 100 150 200 250 300
50
100
150
200
250
160℃
200℃
217
0
70s~120s
40s~60s
Between 1~3℃/S
Preheat Heating Cooling
℃
s
Liquids Temperature
Figure 23: Ramp-soak-spike-reflow of Furnace Temperature
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7.2. Moisture Sensitivity
L76 GNSS module is sensitivity to moisture absorption. To prevent L76 GNSS module from permanent
damage during reflow soldering, baking before reflow is required in following cases:
Humidity indicator card: At least one circular indicator is no longer blue
The seal is opened and the module is exposed to excessive humidity.
L76 GNSS module should be baked for 192 hours at temperature 40℃+5℃/-0℃ and <5% RH in
low-temperature containers, or 24 hours at temperature 125℃±5 ℃ in high-temperature containers. Care
should be taken that plastic tray is not heat resistant. L76 GNSS module should be taken out before
preheating, otherwise, the tray maybe damaged by high-temperature heating.
7.3. ESD Safe
L76 GNSS module is an ESD sensitive device and should be careful to handle.
7.4. Tape and Reel
6
P S
1
12
11
10
9
8
7
6
5
4
3
2
07
06
05
10
09
08
24.00±0.3
11.50±0.15
1.75±0.1
4.00±0.15
? 1.50±0.15
16.00±0.15
0.30±0.05
2.00±0.15
10.10? à0.15
3.00? à0.15
10.10±0.15
11.10±0.15
11.10±0.15
Unit: mm
Quantity per reel: 500pcs
Length per reel: 8.64m
330
28.5
13
100
24.5
Out direction
Figure 24: Tape and Reel Specification
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Table 13: Tray Packing
Model Name
MOQ for MP
Minimum Package:500pcs
Minimum Package x4=2000pcs
L76
500pcs
Size: 370mm×350mm×56mm
N.W: 0.25kg
G.W: 1.00kg
Size: 380mm×250mm×365mm
N.W: 1.1kg
G.W: 4.4kg
7.5. Ordering Information
Table 14: Ordering Information
Model Name
Product Number
Ordering Code
L76
S2-W1087
L76-M33
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8 Appendix Reference
Table 15: Related Documents
SN
Document name
Remark
[1]
L76_EVB _User Guide
L76 EVB User Guide
[2]
L76_GNSS_Protocol_Specification
L76 GNSS Protocol Specification
[3]
L76_Reference_Design
L76 Reference Design
Table 16: Terms and Abbreviations
Abbreviation
Description
AGPS
Assisted GPS
AIC
Active Interference Cancellation
CEP
Circular Error Probable
DGPS
Differential GPS
EASY
Embedded Assist System
EGNOS
European Geostationary Navigation Overlay Service
EMC
Electromagnetic Compatibility
EPO
Extended Prediction Orbit
ESD
Electrostatic Discharge
GPS
Global Positioning System
GNSS
Global Navigation Satellite System
GGA
GPS Fix Data
GLL
Geographic Position – Latitude/Longitude
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GLONASS
GLOBAL NAVIGATION SATELLITE SYSTE
GSA
GNSS DOP and Active Satellites
GSV
GNSS Satellites in View
HDOP
Horizontal Dilution of Precision
IC
Integrated Circuit
I/O
Input /Output
Kbps
Kilo Bits Per Second
LNA
Low Noise Amplifier
MSAS
Multi-Functional Satellite Augmentation System
MOQ
Minimum Order Quantity
NMEA
National Marine Electronics Association
PDOP
Position Dilution of Precision
PMTK
MTK Proprietary Protocol
PPS
Pulse Per Second
PRN
Pseudo Random Noise Code
QZSS
Quasi-Zenith Satellite System
RHCP
Right Hand Circular Polarization
RMC
Recommended Minimum Specific GNSS Data
SBAS
Satellite-based Augmentation System
SAW
Surface Acoustic Wave
TTFF
Time To First Fix
UART
Universal Asynchronous Receiver & Transmitter
VDOP
Vertical Dilution of Precision
VTG
Course over Ground and Ground Speed, Horizontal Course and Horizontal
Velocity
WAAS
Wide Area Augmentation System
Inom
Nominal Current
Quectel
Confidential
GNSS Module
L76 Hardware Design
L76_Hardware_Design Confidential / Released 45 / 45
Imax
Maximum Load Current
Vmax
Maximum Voltage Value
Vnom
Nominal Voltage Value
Vmin
Minimum Voltage Value
VIHmax
Maximum Input High Level Voltage Value
VIHmin
Minimum Input High Level Voltage Value
VILmax
Maximum Input Low Level Voltage Value
VILmin
Minimum Input Low Level Voltage Value
VImax
Absolute Maximum Input Voltage Value
VImin
Absolute Minimum Input Voltage Value
VOHmax
Maximum Output High Level Voltage Value
VOHmin
Minimum Output High Level Voltage Value
VOLmax
Maximum Output Low Level Voltage Value
VOLmin
Minimum Output Low Level Voltage Value
Quectel
Confidential