Contact Us
Log In
Contact Us
Log In
Go to main website
App Develop

App Development

Tuya provides multiple mobile app development methods such as no-code or IoT App SDK development to maximize the monetization of IoT apps.

GUC400 Module Datasheet

Last Updated on : 2021-11-19 06:23:08download

GUC400 is a GNSS positioning module that Tuya has developed. It applies to car navigation, outdoor positioning, and survey and mapping products.

Product overview

GUC400 is a positioning module with the ceramics passive antenna meeting the industry standard of 15 mm×15 mm×4 mm. It includes a highly integrated GNSS chip UFirebird-UC6226NIS and peripheral circuits. Besides, it is further built-in with a SAW filter, an LNA, a 26-MHz TCXO, an SPDT, and other components. The GUC400 module can detect the working status of the external active antenna, has a short-circuit protection mechanism, and can automatically switch between the passive antenna and the active antenna, to ensure fast and precise positioning. It supports both the GPS and Beidou system, to offer users efficient and convenient positioning experiences.


  • Features of location engine:
    • 64-channel synchronous tracking
    • Hot start: <1.2s
    • Cold boot sensitivity: -145 dBm, and tracking sensitivity: -158 dBm
    • Data update rate: Max 10 Hz
  • Support GPS and BDS
    • Use the broad frequency band for RF and the central frequency for input signals is 1575 MHz.
    • Receive and track 1575.42-MHz GPS L1 signals
    • Receive and track 1561.098 MHz BDS B1 signals
    • By default, GUC400 is configured to receive GPS and BDS signals. It can be configured as GPS+BDS, GPS+GLONASS, or a single system through commands. For other systematic configurations, please contact Tuya technical support to obtain the GNSS firmware.
  • Operating voltage: 2.8 to 3.6 V, typ. 3.3V
  • Built in with a 26-MHz TCXO
  • Protocol and interface: GUC400 complies with the Unicore Protocol Specification. It communicates with the host device based on the UART.
  • Operating temperature: -40℃ to +85℃

Change history

Update date Updated content Version after update
11/12/2021 This is the first release. V1.0.0

Module interfaces

Pin distribution

GUC400 has 2 lines of pins with a 1.54-mm pin spacing. Each line has 12 pins.

  • The dimensions of GUC400:

    • 16 ± 0.35 mm (W)
    • 16 ± 0.35 mm (L)
    • 7.05 ± 0.15 mm (H)
  • Thickness of PCB: 0.8±0.1 mm

    GUC400 Module Datasheet

Pin definition

Pin number Symbol Signal type Description
1 RXD I Serial interface for receiving data, which is used to input PMTK/PQ commands and upgrade firmware
2 TXD O Serial interface for transmitting data, which is used to output NMEA sentences
3 GND Ground
4 VCC PI The interface of the main power supply
5 V_BCKP PI The interface of the backup power supply
6 1PPS O PPS stands for Pulse Per Second
7 NC No connected
8 ADET_N O The interface for detecting the working status of the external active antenna. If not used, disconnected.
9 NC No connected
10 RST I Reset pin. Low active.
11 EX_ANT I The interface for inputting RF signals of the external active antenna. If not used, disconnected.
12 GND Ground

Note: P indicates a power supply pin and I/O indicates an input/output pin.

Electrical parameters

Absolute electrical parameters

Parameter Description Minimum value Maximum value Unit
Ts Storage temperature -40 90
VCC Supply voltage -0.2 3.6 V
ESD voltage (human body model) TAMB-25℃ TBD KV
ESD discharge voltage (machine model) TAMB-25℃ TBD KV

Normal working conditions

Parameter Description Minimum value Typical value Maximum value Unit
Ta Operating temperature -40 25 85
VCC Supply voltage 2.8 3.3 3.6 V
V_BCKP Backup voltage 1.4 3.3 3.6 V

Power consumption in operating mode

Operating mode Type Average value Peak value (typical value) Unit
Capture VDCDC_IN current 31.23 41.18 mA
Track VDCDC_IN current 31.15 40.77 mA

Note: The test voltage for VDCDC_IN is 3.3 V and the latest firmware version R3.1.10.0 Build 6582. A built-in ceramics antenna is adopted.

Main performance parameters

Parameter Conditions Indicator Unit
CN0 The signal strength of the stimulator: -130 dBm (AVG) 40±2 dBc
TTFF (the module is static state in the open environment) Cold boot/hot start/recapture 30/1.2/2 s
Sensitivity test Capture sensitivity/tracking sensitivity -145/-158 dBm
Positioning precision Remain static in the open area CEP50 2.5 m
Internal passive ceramics antenna Characteristic impedance of 50 Ω, a gain of 1.5dB, VSWR≤1.5
External active antenna Antenna provided by the third party with the characteristic impedance of 50Ω

Antenna information

By default, the GUC400 module receives signals in the frequency band GPS L1 (1575.42 Mhz) and frequency band BDS B1 (1561 MHz). The module has a passive ceramics antenna of 15 mm×15 mm×4 mm. Meanwhile, it also supports the external active antenna. The module can automatically switch between the two antennas with the internal SPDT.

15×15×4 internal ceramics antenna

The GUC400 module has a passive ceramics antenna with the specifications of 15 mm×15 mm×4 mm. Its performance is critical to the reception sensitivity of the whole GNSS. The specifications of the antenna of module GUC400 are as follows:

Parameter Specifications Remarks
Dimensions 15mm×15 mm×4mm
Frequency range of receiving 1561-1575 ± 2.5 MHz Central frequency1568 ± 3 MHz
Characteristic impedance 50 Ω
Band width Min. 20 MHz Return loss ≤ -10 dB
Frequency temperature coefficient 0 ± 10 ppm /℃ -40 ℃ to 85 ℃
Polarization RHCP Right hand circular polarization
Gain Typ. 1.5 dBi
Axial ratio Max. 5 dB
VSWR Max. 1.5

The test results of the antenna are as follows:

GUC400 Module Datasheet

Instructions on PCB

The radiation performance of the antenna is easily affected by various factors, such as the size and shape of the PCB, and the dielectric constant of the components near the antenna. Please follow the following advice during the layout of the PCB:

  • The module should be at least 5mm away from the edge of the mother board. You’d better put it at the centre of the mother board.
    GUC400 Module Datasheet

  • It is recommended that you make a hole at the connection point of the mother board and the antenna of the module. The diameter of the hole should be not less than 2.5 mm.
    GUC400 Module Datasheet

  • It must be ensured that the antenna faces the sky without shading.

  • The performance of the ceramics passive antenna is affected by the size of the ground around it. So you’d better maintain a complete ground with the size of 30 mm × 30 mm under the antenna, which is shown below: Moreover, you should not put another component (especially a large component or a component that has the radiation and interference capability) and make another hole in the ground.
    GUC400 Module Datasheet

  • The distance between the antenna and elements that have a metal housing and are high enough should not be less than 10 mm.
    GUC400 Module Datasheet

  • The MCU, crystal, LCD, camera, and other high-speed components and interfaces should be placed in the opposite direction of the module and kept away from the module as much as possible.
    GUC400 Module Datasheet

  • The wiring of the USB, LCD, camera, and crystal and the hole should be at the inner layer of the mother board and separated from the module with the ground. That is, keep away from the module as much as possible.

  • The DCDC must keep away from the module.

  • The housing of devices (especially the materials around the antenna) should be made of non-metal materials, and the distance between it and the antenna should be at least 3 mm.

  • As the RF part of the GNSS module is sensitive to temperature, the module should keep away from the heating source.

External active antenna

The connection between the external active antenna and the GUC400 module is designed as below: The DC in the EX_ANT pin of the module can be directly supplied to the external active antenna. In this design, the RF link should be as short as possible, and the characteristics impedance should be strictly controlled at 50 Ω. R1, C1, and C2 are reserved for impedance matching. By default, C1 and C2 are NC, and R1 is 0R. It should be noted that R1 mustn’t be a capacitor, because the current flows to the antenna via R1; and the C1 and C2 cannot be inductance or resistance, to avoid short circuit.

GUC400 Module Datasheet

Active antenna Recommended specifications
Operating frequency L1: 1575.42±1.023 MHz; B1: 1561±2.046 MHz
Band width > 20 MHz
Polarization RHCP
Characteristic impedance 50 Ω
Noise factor ≤ 1.5
Gain (Ceramics antenna) 5 dBic (Put onto a test mother board of 70 mm×70 mm)
Gain (Internal LNA)) 28±3 dB
Current consumption 9±3 mA (3.3V)

Detection of status of external active antenna

The GUC400 module can detect the status of the external active antenna, and switch between the internal and external antennas according to the status of the external antenna. You can query the status of the external active antenna by sending $ANTSTAT sentences to the module via the UART interface.

Status of the external antenna OPEN_DET SHORT_DET Level of Pin ADET_N (Control via SPDT) Message returned by the module
Open circuit 1 0 1 (Switch to the internal antenna) $ANTSTAT,1,0
Short circuit 0 1 1 (Switch to the internal antenna) $ANTSTAT,0,1
Normal 0 0 0 (Switch to the external antenna) $ANTSTAT,0,0


  • If the module returns the sentence of $ANTSTAT,1,0, it indicates that the external antenna is not connected or falsely soldered, and the module will automatically switch to the internal ceramics passive antenna.
  • If the module returns the sentence of $ANTSTAT,0,1, it indicates that the external antenna is short-circuited, and the module will automatically switch to the internal ceramics passive antenna and cut off the power supplied from the EX_ANT pin.
  • If the module returns the sentence of $ANTSTAT,0,0, it indicates that the external antenna is normal and the module will automatically switch to the external antenna.

Packaging information and production instructions

Mechanical dimensions

Mechanical dimensions of GUC400 (unit: mm)
GUC400 Module Datasheet

Note: The default outline dimension tolerance is ±0.35 mm, and the critical dimension tolerance is ±0.1 mm. If you have specific requirements on dimensions, make them clear in the module datasheet after communication.

Bottom view and recommended footprint

Bottom view of GUC400 (unit: mm)

GUC400 Module Datasheet

Recommended footprint (unit: mm)

GUC400 Module Datasheet

Production instructions

  1. The Tuya SMT module should be mounted by the SMT device. After being unpacked, it should be soldered within 24 hours. Otherwise, it should be put into the drying cupboard where the RH is not greater than 10%; or it needs to be packaged under vacuum again and the exposure time needs to be recorded (the total exposure time cannot exceed 168 hours).
    • SMT devices:
      • Mounter
      • SPI
      • Reflow soldering machine
      • Thermal profiler
      • Automated optical inspection (AOI) equipment
    • Baking devices:
      • Cabinet oven
      • Anti-electrostatic and heat-resistant trays
      • Anti-electrostatic and heat-resistant gloves
  2. Storage conditions for a delivered module:
    • The moisture-proof bag must be placed in an environment where the temperature is below 40°C and the relative humidity is lower than 90%.

    • The shelf life of a dry-packaged product is 12 months from the date when the product is packaged and sealed.

    • There is a humidity indicator card (HIC) in the packaging bag.

      GUC400 Module Datasheet

  3. The module needs to be baked in the following cases:
    • The packaging bag is damaged before unpacking.
    • There is no HIC in the packaging bag.
    • After unpacking, circles of 10% and above on the HIC become pink.
    • The total exposure time has lasted for over 168 hours since unpacking.
    • More than 12 months has passed since the sealing of the bag.
  4. Baking settings:
    • Temperature: 60°C and ≤ 5% RH for reel package and 125°C and ≤5% RH for tray package (please use the heat-resistant tray rather than plastic container)
    • Time: 48 hours for reel package and 12 hours for tray package
    • Alarm temperature: 65°C for reel package and 135°C for tray package
    • Production-ready temperature after natural cooling: < 36°C
    • Re-baking situation: If a module remains unused for over 168 hours after being baked, it needs to be baked again.
    • If a batch of modules is not baked within 168 hours, do not use the reflow soldering to solder them. Because these modules are Level-3 moisture-sensitive devices, they are very likely to get damp when exposed beyond the allowable time. In this case, if they are soldered at high temperatures, it may result in device failure or poor soldering.
  5. In the whole production process, take electrostatic discharge (ESD) protective measures.
  6. To guarantee the passing rate, it is recommended that you use the SPI and AOI to monitor the quality of solder paste printing and mounting.

Recommended oven temperature curve

Set oven temperatures according to the following temperature curve of reflow soldering. The peak temperature is 245°C.

GUC400 Module Datasheet

  • A: Temperature axis

  • B: Time axis

  • C: Liquidus temperature: 217 to 220°C

  • D: Ramp-up slope: 1 to 3°C/s

  • E: Duration of constant temperature: 60 to 120s; the range of constant temperature: 150 to 200°C

  • F: Duration above the liquidus: 50 to 70s

  • G: Peak temperature: 235 to 245°C

  • H: Ramp-down slope: 1 to 4°C/s

    Note: The above curve is just an example of the solder paste SAC305. For more details about other solder pastes, please refer to Recommended oven temperature curve in the solder paste specifications.

Storage conditions

GUC400 Module Datasheet

MOQ and packaging information

Product model MOQ (pcs) Shipping packaging method The number of modules per reel The number of reels per carton
GUC400 1600 Tape reel 400 4