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• $BQ25504RGTT$: This is the heart of the project, serving as the power management IC. It is responsible for boosting the input voltage from the solar cells and managing the charging and discharging cycles of the capacitor or battery.
• Solar Cells ($SC1$, $SC2$, $SC3$, $SC4$): These components generate power from sunlight, which is the primary energy source for the device.
• $WM1110$ Module: This likely refers to a wireless communication module used for data transmission in applications such as animal tracking.
• Capacitors and Inductors: Various capacitances are used throughout the circuit for smoothing, energy storage, and filtering. Inductors like $L90$ are part of the boost converter circuit, helping to step up the input voltage.
• Resistors: Serve different functions including setting thresholds for the $BQ25504$ (e.g., over-voltage protection with resistors like $R9$ and $R10$) and tuning other parameters.
• Diodes ($D1$, $D2$, etc.): Used for rectification, blocking reverse currents, and routing power.
• Connectors ($J2$, $J4$): These provide interfaces for external connections.

• V_SOLAR, VBAT, VSTOR, etc.: These nets denote the various power paths within the system. V_SOLAR connects the solar panels to the input of the $BQ25504$, VBAT is the output storage, and VSTOR represents the net that connects to the storage or load from the boost converter.

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• Power Management and Conversion:

  • The BQ25504RGTT IC is used for energy harvesting and battery management. It interfaces with various nets for optimal battery management, such as over-voltage $VBAT_{OV}$ and under-voltage $VBAT_{UV}$ protection.
  • Solar cells such as SC1 and SC2 convert solar energy into electrical energy.

• Energy Storage:

  • A hybrid lithium-ion capacitor (such as those typically indicated by designators like C1) is used to store energy.

• Boost Converter:

  • The BQ25504RGTT steps up the voltage from the solar cells to charge the storage capacitor. Key nets such as $V_{STOR}$ and $V_{REF_SAMP}$ are connected to this IC for performance enhancements.

• Voltage Regulation:

  • The AMS1117-3.3 is used to regulate the output to 3.3V, suitable for powering modules connected to the circuit.

• Inductors and Capacitors:

  • Several inductors (L90, L4) and capacitors (C13, C17) are used throughout for filtering and stabilizing voltages and currents.

• Diodes:

  • Multiple BAT60JFILM diodes (D1, D6) are used for rectification and protection against reverse polarity.

• Resistors and Resistor Networks:

  • Resistor networks are crucial for setting thresholds and biases in circuits, such as voltage dividers for sensing voltage levels (e.g., R9, R10).

• Antenna Connections:

  • Connectors like the U.FL connectors J2 are used for connecting antennas to the WM1110 module for communication purposes.

• GND connections are prevalent throughout the design, ensuring all components have a common return path.
• Many nets are excluded from the bill of materials or PCB; these are probably used for simulation or internal purposes and won't appear in the final design or cost sheet.
• The design employs a systematic approach to manage and regulate power effectively, leveraging a modular design strategy with separate components for distinct functionalities.

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1. WM1110 Module:

   • This module typically requires careful attention to digital IO pins, especially for communication interfaces such as UART, I2C, or SPI.
   • For I2C lines (if utilized), ensure SDA and SCL have pull-up resistors if they are not internally pulled up.
   • Unused GPIOs can often be left floating, but consult the Seeed Studio documentation to determine if any need tying down to prevent unwanted operation.

2. BQ25504RGTT Boost Converter:

   • Check the pins like VIN, VOUT, and control pins like VBAT_OK or VREF_SAMP. Often VREF, for instance, might need specific resistor setups based on application requirements.
   • Refer to its datasheet to explore any configuration pins that should not be left floating.

3. Common Considerations:

   • Digital Inputs: Typically need pull-up or pull-down resistors if not driven. This prevents the pins from picking up noise and causing unexpected behavior.
   • Unused Pins: Confirm through datasheets if they can be safely left floating or need grounding.

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1. Component Duplication and Naming:

   • The component BQ25504RGTT is mentioned multiple times with different designator prefixes (e.g., U57, U2). Ensure that each instance is unique and serves a distinct purpose in your design, or check for naming errors.

2. Partially Defined Components:

   • Some components are missing details such as manufacturer part numbers (MPNs) and manufacturer names (e.g., C13, R4). This can be problematic when ordering parts. Review and clarify these components.

3. DNP (Do Not Populate) Components:

   • Several components are marked as DNP (e.g., R16, C16, R13). Ensure these are intentionally excluded and do not affect circuit functionality. Be cautious if they are needed for debug or future-proofing.

4. Net Connections:

   • Ensure all nets (e.g., VBAT, 3V3, etc.) are correctly connected and that there are no floating pins unless explicitly intended.

5. Grounding:

   • Check that all intended ground connections are correctly connected to the GND net.

6. Voltage Levels:

   • Ensure the voltage levels between different stages (input and output) are compatible, particularly when using different voltage domains.

7. Power Supply Considerations:

   • Make sure that the solar power and boost converter design can sufficiently handle the required current and voltage for the $WM1110$.

8. Licenses and Exclusions:

   • Verify that any licensing requirements are understood and met. Components marked with "Exclude from BOM" or "Exclude from PCB" may not be accounted for in assembly or costing; ensure this is intentional.

9. Undefined Route Points:

   • There are undefined route branch points in the project. Make sure these are specified to prevent signal integrity issues or unexpected behaviors.

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1. Follow Manufacturer Guidelines: Refer to datasheets for recommended land patterns and spacing for each component. Manufacturers often provide details on optimal positioning to enhance heat dissipation and mechanical stability.
2. Thermal Management: Ensure adequate spacing for heat-sensitive components. For example, components like the AMS1117-3.3 may require additional thermal relief.
3. Signal Integrity: Maintain necessary signal traces and avoid crossing sensitive routes with noisy power lines. Components should be spaced to minimize loop areas and prevent electromagnetic interference.
4. High-Frequency Considerations: Utilize close placement for components in high-frequency paths to minimize inductance and maintain good RF performance, especially for components like the BGA524N6.
5. Manufacturing Constraints: Ensure enough spacing between components for manufacturability, including soldering and assembly processes. SMD components like resistors and capacitors should comply with IPC standards.
6. Testing and Debugging: Allow space for test points and debugging access. This helps in troubleshooting during both development and production stages.
7. Ground Return Paths: Keep return paths short and direct, especially for components connected to ground, such as those with multiple ground pins or pads.

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1. Power Path:

   • Ensure connections are correct from the solar cells (e.g., $SC1$) to the BQ25504RGTT (VIN_DC) and through to the storage elements like capacitors and batteries.

2. Connections:

   • Connect Solar Input: SC1:(+) to V_SOLAR:$P1$ and then to U57:$VIN_DC$.
   • Connect Output Storage: U57:$VSTOR$ to storage capacitors like $C2$ and $C3$.

3. Battery Management:

   • Ensure over-voltage (OV) and under-voltage (UV) networks are correctly set up.
   • Connect U57:$VBAT_OV$ using components $R9$ and $R10$.
   • Similarly, connect U57:$VBAT_UV$ using $R11$ and $R12$.

4. Grounding:

   • All GND pins for components and nets should be correctly connected. Verify that all components intended to connect to the ground are part of the GND net.

5. Power Conditioning:

   • Ensure the bypass capacitors like $C1$ and $C21$ are placed close to the ICs they're intended to decouple.

6. Diodes:

   • Ensure you have placed schottky diodes like $D1$ for reverse polarity protection or feedback loops correctly in the power circuit.

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1. Choose a USB-C Connector:

   • Look for a USB-C connector with a compatible footprint that can handle the required signal and power lines. It's recommended to select a part that suits your board layout and has enough mechanical stability.

2. Update Schematic and Connections:

   • Disconnect Existing USB Jack: Remove connections from $J3$ (Pins: VBUS, D-, D+, GND).
   • Add USB-C Connector in Schematic: Place the new USB-C connector in your schematic.

3. Re-assign Connections to USB-C:

   • Connect the VBUS pin to the same net as the current VBUS.
   • Connect GND to the same ground net.
   • Connect D- and D+ to the respective nets.
   • If your USB-C connector has additional pins such as CC (Configuration Channel), they may need to be connected to configure the cable for power delivery and USB 2.0 operations.
   • Connect the shield pins to GND, if present.

4. Layout Considerations:

   • Ensure the new footprint fits within your PCB layout.
   • Consider USB 2.0 signal integrity requirements for D- and D+ routing.
   • If using power delivery features, ensure correct routing and components for CC handling.

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• Microcontroller: WM1110 from Seeed Studio.
• Power Management: Using BQ25504RGTT.
• Regulator: AMS1117-3.3 providing a 3.3V output.
• Diodes: BAT60JFILM for voltage protection or rectification.
• Interfaces: Current USB connector for communication/powering needs to be replaced with USB-C.

1. Footprint Compatibility: Ensure the footprint of the USB-C matches or can be adapted to your PCB layout.
2. Power & Signal Connections:

   • Check if VBUS, D+, and D- are correctly routed.
   • Add CC line handling if needed for proper USB-C configuration.
   • Make sure that the ground and shield connections are made properly.

3. Signal Integrity: Ensure proper routing for the D+ and D- lines respecting USB 2.0 specifications.
4. Power Regulation: Confirm that the voltage lines are within the limits recommended by the corresponding ICs and that the BQ25504 is correctly configured for battery management.
5. Component Values: Verify resistor, capacitor values, and other passive components align with the power requirements of the microcontroller and peripherals.

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1. BQ25504RGTT

   • Power Net: Not explicitly mentioned.
   • Decoupling Capacitors:

     • C1: $100 , \mu\text{F}$
     • C2: $4.7 , \mu\text{F}$
     • C3: $0.1 , \mu\text{F}$
     • C4: $4.7 , \mu\text{F}$
     • C5: $0.1 , \mu\text{F}$
     • C6: $0.01 , \mu\text{F}$

   • Conditions:

     • Voltage rating of attached capacitors not stated: [WARNING]

2. U3 - BGA524N6

   • Power Net: Net 11
   • Decoupling Capacitors:

     • C12: $1 , \text{nF}$
     • C13: $1 , \text{nF}$

   • Conditions:

     • Voltage rating of attached capacitors not stated: [WARNING]

3. U1 - WM1110

   • Power Nets:

     • VDD_LR_22, VDD_LR_21 (Net 17)
     • VDD_NRF_27, VDD_NRF_28 (Net 9)

   • Decoupling Capacitors:

     • Net 17:

       • C11: $100 , \text{nF}$
       • C17: $10 , \mu\text{F}$

     • Net 9:

       • C19: $100 , \text{nF}$
       • C20: $10 , \mu\text{F}$

   • Conditions:

     • Voltage rating of attached capacitors not stated: [WARNING]

4. U5 - RFECA3216060A1T

   • Conditions:

     • No decoupling capacitors are attached: [WARNING]

5. U4 - M04-0103010R0A

   • Conditions:

     • No decoupling capacitors are attached: [WARNING]

6. U2 - MD1506-12N

   • Conditions:

     • No decoupling capacitors are attached: [WARNING]

• Ensure the voltage ratings of all decoupling capacitors are specified to avoid voltage mismatch.
• Certain ICs lack decoupling capacitors, such as U5, U4, and U2, which could compromise performance or stability.

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1. U5 - RFECA3216060A1T

   • Decoupling Capacitors Recommendation:

     • C21: Add a capacitor of $0.1 , \mu\text{F}$ connected to the power pin of U5.
     • C22: Add a capacitor of $10 , \mu\text{F}$ to provide additional energy storage.

   • Connections:

     • Connect U5:Soldering terminal to C21:P1 and C22:P1.
     • Connect C21:P2 and C22:P2 to GND.

2. U4 - M04-0103010R0A

   • Decoupling Capacitors Recommendation:

     • C23: Add a capacitor of $0.1 , \mu\text{F}$ connected to the power pin of U4.
     • C24: Add a capacitor of $10 , \mu\text{F}$ for additional energy storage.

   • Connections:

     • Connect U4:P1 to C23:P1 and C24:P1.
     • Connect C23:P2 and C24:P2 to GND.

3. U2 - MD1506-12N

   • Decoupling Capacitors Recommendation:

     • C25: Add a capacitor of $0.1 , \mu\text{F}$ connected to the power pin of U2.
     • C26: Add a capacitor of $10 , \mu\text{F}$ for additional energy storage.

   • Connections:

     • Connect U2:P1 to C25:P1 and C26:P1.
     • Connect C25:P2 and C26:P2 to GND.

• If the ICs have specific power pins or terminals, use those for the connection.
• These decoupling capacitors should be placed as close as possible to the power pins of the ICs to minimize inductance and resistance in the power path.
• Make sure to verify the voltage ratings for these capacitors to ensure they are appropriate for your circuit voltage.

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1. Component Selection:

   • Resistors and Capacitors: Double-check if you can use more common, less precise, or higher tolerance parts that generally cost less.
   • Inductors: Select inductors with slightly different specifications if they meet functional requirements, allowing for potentially cheaper options.
   • Diodes and Ferrite Beads: Consider alternatives if current parts are over-specified for your requirements.

2. Quantity Discounts:

   • Purchase components that offer discounts at higher quantities from distributors.

3. Alternative Suppliers:

   • Review pricing from different distributors such as Digi-Key, Mouser, Arrow, and LCSC to find more competitive prices.

4. Optimize PCB Design:

   • Layout Optimizations: Improve trace layout to reduce the number of vias and board layers if applicable.
   • Board Size: Reduce overall board size to decrease fabrication costs.

5. Removing or Modifying Components:

   • Check if resistors labeled as "DNP" (Do Not Populate) like some in your design can be, indeed, omitted in the production version if they are truly unnecessary.
   • Review the necessity of all components and ensure each one serves a critical purpose.

6. Reduce Assembly Complexity:

   • Use standard packages (e.g., SMD 0603) for easier assembly and cost efficiency.
   • Consolidate similar components to reduce unique part counts.

7. Evaluate Power Solutions:

   • Ensure that your power solution is well-optimized for cost versus efficiency. The $BQ25504RGTT$ is a relatively high-cost component; evaluate if it's essential or if another IC could fulfill your requirements at a lower cost.

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• BM1110 Module (U1)

  • This module integrates GPS and LoRa capabilities.
  • Multiple ground pins ($GND$) and voltage supply pins ($VDD\_LR$).

• Power Management Unit (PMU) (U57)

  • The BQ25504RGTT handles power harvesting from solar panels and regulates the power for the system.
  • Several key pins include:

    • VIN_DC: Input from solar panels.
    • VBAT: Connection to the battery.
    • VSTOR: Storage element connection.
    • LBST: For low battery indication.

• Solar Panels (SC1, SC2, SC3, SC4)

  • SM141K04LV solar panels are used for harvesting energy.

• Capacitors and Resistors

  • Various capacitors ($C1$, $C2$, ... etc.) and resistors ($R1$, $R2$, ... etc.) are used for filtering and dividing voltages.

• Diodes

  • BAT60JFILM diodes prevent reverse current.

• Solar Panels to PMU

  • Connect SC1:(+) to D1:(A)
  • Connect D1:(K) to $VIN\_DC$ of $U57$.

• Hybrid Lithium-Ion Capacitor (HLIC)

  • Connect $VBAT$:(P1) to $VBAT$ of $U57$.

• Power Storage

  • Connect $VSTOR$:(P1) to $VSTOR$ of $U57$.
  • Include capacitors $C2$ and $C3$ for voltage stabilization at VSTOR.

• Voltage Division and Reference Sampling

  • Create a voltage divider using resistors $R5$ and $R6$, and connect to $VRDIV$ of $U57$.
  • Connect the reference sample to VOC_SAMP of $U57$, using $R4$ and $R5$.

• Resistor and Capacitor Values: You may need to tweak the values according to specific requirements and available components.
• Inductance and Filtering: Ensure proper filtering using inductors $L1$, $L3$, etc., and capacitors to maintain signal integrity.

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• C7: A bypass capacitor with 40μF capacitance and 3.8V maximum reverse voltage.

1. Ground Connection:

   • Connect C7:K to GND.

2. Voltage Connection:

   • Connect C7:A to the main input voltage rail. In this case, we can assume that the main voltage input is the solar panel input net (Net$D5-K$), which connects to the VIN_DC of U57.

• Connect C7:A to U57:VIN_DC.
• Connect C7:K to GND.

• Connect C7:A to U57:VIN_DC.
• Connect C7:K to GND.

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• C7: Serves as an energy storage capacitor, which will be connected across the power supply.

1. Ground Connection:

   • Connect C7:K (cathode) to GND.

2. Voltage Connection:

   • Connect C7:A (anode) to the main voltage storage node, which is VSTOR in your schematic as it provides the regulated output voltage.

• Connect C7:A to U57:VSTOR.
• Connect C7:K to GND.

• Connect C7:A to U57:VSTOR.
• Connect C7:K to GND.

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• For a fully charged state, VBAT could be around 3.8V.
• For a discharged state, VBAT might go down to around 2.2V.

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• Nominal Voltage (VBAT): Typically around 3.7V.
• Fully Charged Voltage: Up to 4.2V.
• Discharged Voltage: Down to 2.2V.

• Operational Range for VBAT: 2.2V to 5.2V.
• UV (Undervoltage) Setting: Configurable, often set around 2.4V to 3.0V.
• OV (Overvoltage) Setting: Configurable, typically set around 4.2V.

• Nominal Voltage (VBAT): $3.7V$
• Fully Charged Voltage: $4.2V$

• VBAT:P1 connects to U57:VBAT
• C7:A (Hybrid Lithium-Ion Capacitor Anode) connects to U57:VSTOR
• C7:K (Hybrid Lithium-Ion Capacitor Cathode) connects to GND

1. Nominal Voltage: $VBAT = 3.7V$
2. Fully Charged Voltage: $VBAT_{charged} = 4.2V$
3. Minimum Operational Voltage: $VBAT_{min} = 2.2V$

• VBAT_NET Configuration:

  • VBAT: $3.7V$
  • VBAT_{charged}: $4.2V$
  • VBAT_{min}: $2.2V$