• 2 × I2S interfaces

• The ESP32-S3-WROOM-1-N8R8 supports 2 I2S interfaces.
• You can connect up to 2 I2S microphones.

• Connect MK1:WS to U1:IO13 (Net: Net 6).
• Connect MK1:LR to U1:IO42 (Net: Net 1).
• Connect MK1:GND to GND (Net: GND).
• Connect MK1:SCK to U1:IO14 (Net: Net 8).
• Connect MK1:VDD to PP3V3 (Net: Net 13).
• Connect MK1:SD to U1:IO15 (Net: Net 10).

• LR Pin (Left/Right Select): This pin determines whether the microphone outputs its data on the left or right channel of the I2S bus.
  • If the LR pin is connected to ground (GND), the microphone outputs its data on the left channel.
  • If the LR pin is connected to the power supply (VDD), the microphone outputs its data on the right channel.

• To set MK1 to the left channel, connect MK1:LR to GND.
• To set MK1 to the right channel, connect MK1:LR to VDD.

• Connect THERMISTOR:P1 to U3:TS.
• Connect THERMISTOR:P2 to U3:VSS.

1. Connect BATT CONN:P1 to $U3$:BAT_1.
2. Connect BATT CONN:P1 to $U3$:BAT_2.
3. Connect BATT CONN:P2 to $U3$:VSS.

• $ V_{OUT} $ = 3.3V
• Suggested value for RF2 is between 50kΩ and 100kΩ

Python
# Given values
V_out = 3.3  # V
V_ref = 1.24  # V (reference voltage for LM2623)
RF2 = 100e3  # Ohms

# Calculate RF1 using the provided formula
RF1 = RF2 * ((V_out / V_ref) - 1)
RF1

• RF2 = 100kΩ
• RF1 = 166.1kΩ

• The switching frequency is selected by choosing an external resistor connected between the VIN pin and the FREQ pin.
• The frequency range can be set between 300 kHz to 2 MHz, allowing the use of very small surface-mount inductors and capacitors.

1. Determine the desired switching frequency: Based on your application requirements, choose the desired switching frequency within the recommended range of 300 kHz to 2 MHz.
2. Refer to the graph/table: Look at Figure 3 in the typical characteristics section of the LM2623 datasheet to find the relationship between the frequency and the resistor value.

• Desired frequency, $f_{SW} = 1$ MHz
• Corresponding resistor, $R_3 = 47$ kΩ

• Connect R3:P1 to U2:VIN.
• Connect R3:P2 to U2:FREQ.

• LRCLK (Left-Right Clock):
  • Connect MK2:LR to U1:IO42 (Net 5).
• BCLK (Bit Clock):
  • Connect MK2:SCK to U1:IO45 (Net 7).
• DATA:
  • Connect MK2:SD to U1:IO47 (Net 11).
• Power Supply:
  • Connect MK2:VDD to PP3V3:P1 (Net 13).
• Ground:
  • Connect MK2:GND to GND:GND.

• Connect MK2:LR to U1:IO42.
• Connect MK2:SCK to U1:IO45.
• Connect MK2:SD to U1:IO47.
• Connect MK2:VDD to PP3V3:P1.
• Connect MK2:GND to GND:GND.

1. Input Capacitor (CIN): Usually a ceramic capacitor placed between the input pin (IN) and GND.
2. Battery Capacitor (CBAT): Typically a capacitor placed between the BAT pin and GND.
3. Output Capacitor (COUT): A capacitor placed between the output pin (OUT) and GND.
4. ILIM Resistor: Resistor connected to the ILIM pin to set the input current limit.
5. ISET Resistor: Resistor connected to the ISET pin to set the charge current.
6. Thermistor (optional): Connected to the TS pin for battery temperature monitoring.
7. Status LEDs (optional): Connected to PGOOD and CHG pins for status indication.

• Input Capacitor
  • Connect C7:P2 to U3:IN and C7:P1 to GND (Implemented as Net 20).
• Battery Capacitor
  • Connect C8:P2, C9:P2 to U3:BAT_1, U3:BAT_2 and their other pins to GND (Part of Net 22).
• Output Capacitor
  • Connect U3:OUT_1, U3:OUT_2 to a capacitor, C10:P2 to Net 22. Also ensure another side is connected properly to GND.
• ILIM Resistor
  • R5 with a resistance value of 150k is connected to the ILIM pin (part of Net 22).
• ISET Resistor
  • R4, R3 in Net 21, connected on one side to ISET, other to ground.
• Thermistor
  • Net 4 indicates presence of a thermistor (THERMISTOR:P2 grounding to U3:TS with a pull-up to a higher voltage).
• Status LEDs (optional)
  • It appears there’s no explicit connection for status indicators LEDs to PGOOD and CHG. Potentially could add a LED implementation through appropriate resistors for user visibility of charging status.

• Make sure that all capacitors and resistors are connected correctly and validate that their values match the design considerations provided in the BQ24075RGTT datasheet.
• Ensure proper PCB layout guidelines for power routing, thermal conductivity, and signal integrity around critical components.
• Consider adding status indicators if real-time user-feedback on charge status is required.

• $V_{ILIM}$ is the reference voltage at the ILIM pin (typical value is 1V).
• $I_{IN_LIMIT}$ is the desired input current limit.

1. Input Capacitor (IN to Ground):
   • A capacitor (usually around 10uF to 22uF) to filter the input power.
   • Connect the positive terminal of the capacitor to U3:IN and the negative terminal to ground (GND).
2. Output Capacitors (OUT to Ground):
   • Capacitors (typically in the range of 10uF to 22uF) to stabilize the output voltage.
   • Connect the positive terminals of the capacitors to U3:OUT_1 and U3:OUT_2, and the negative terminals to ground (GND).
3. Thermistor (for battery temperature sensing):
   • A 10k thermistor between the TS pin and ground.
   • Connect one end of the thermistor to U3:TS and the other end to ground (GND).
4. Current Limiting Resistor (ILIM to Ground):
   • A resistor to set the input current limit.
   • Connect one end of the resistor to U3:ILIM and the other end to ground (GND).
5. Charge Current Set Resistor (ISET to Ground):
   • A resistor to set the charge current.
   • Connect one end of the resistor to U3:ISET and the other end to ground (GND).
6. Timer Capacitor (TMR to Ground):
   • A capacitor to set the safety timer duration.
   • Connect one end of the capacitor to U3:TMR and the other end to ground (GND).
7. Battery Connector:
   • The battery pack should be connected to U3:BAT_1 and U3:BAT_2.
8. Enable Pins:
   • The enable pins (EN1 and EN2) can be tied according to the configuration needed for your application. They are usually connected to logic high (3.3V) or low (GND).

• Power Connections:
  • Connect U3:IN to your 5V power source.
  • Connect U3:OUT_1 and U3:OUT_2 to your system's load (e.g., 3.3V rail).
• Ground Connections:
  • Connect U3:VSS, U3:VSS_THERMAL_PAD, capacitor grounds, and thermistor ground to GND.

1. Connect input capacitor: Connect the positive terminal of the 22uF capacitor to U3:IN and the negative terminal to GND.
2. Connect output capacitors: Connect the positive terminals of the 10uF capacitors to U3:OUT_1 and U3:OUT_2, and the negative terminals to GND.
3. Connect thermistor: Connect one end of the 10k thermistor to U3:TS and the other end to GND.
4. Connect ILIM resistor: Connect one end of the resistor to U3:ILIM and the other end to GND.
5. Connect ISET resistor: Connect one end of the resistor to U3:ISET and the other end to GND.
6. Connect TMR capacitor: Connect one end of the capacitor to U3:TMR and the other end to GND.
7. Connect battery terminals: Connect the battery pack to U3:BAT_1 and U3:BAT_2.

• Pin 18 is labeled as IO19 and functions as USB D+
• Pin 19 is labeled as IO20 and functions as USB D-

• U1 is USB D+
• U1 is USB D-.

• Pin 19 $(\text{IO20})$: RTC_GPIO20, GPIO20, U1CTS, ADC2_CH9, CLK_OUT1, USB_D+[1]
• Pin 18 $(\text{IO19})$: RTC_GPIO19, GPIO19, U1RTS, ADC2_CH8, CLK_OUT2, USB_D-

1. Capacitor Placement:
   • Ensure that the output capacitor ($C6$, $C8$, $C9$, $C10$, $C12$, $C13$, $C14$, and $C15$) is physically close to the inductor and the diode. This minimizes the inductance and resistance in the current path, which could cause voltage spikes.
2. Capacitor Value:
   • The value of the output capacitance should be chosen to meet the ripple requirements and stability criteria. It is also important that the capacitors can handle high-current pulses generated by the discharge process of the inductor.
3. Current Handling Capability:
   • The output capacitor will experience high-current steps from 0 to $I_{PEAK}$ each time the switch turns off and the Schottky diode turns on. Ensure the capacitors can handle such peaks and have a low ESR (Equivalent Series Resistance) to support this operation.
4. Capacitor Type:
   • You should use stable materials for the output capacitors like X7R or X5R ceramic capacitors to maintain consistent capacitance over voltage and temperature changes.
5. Avoiding Voltage Spikes:
   • Verify that there is minimal inductance along the series path from the diode's cathode, through the output capacitor, and back into the LM2623 GND pin to prevent voltage spikes that can over-voltage the SW and BOOST pins or feed through to the ground.

• Check Net Connections:
  • Connect the cathode of $D1$:K to $C6$:P1, $C8$:P1, $C9$:P1, $C10$:P1, $C12$:P1, $C13$:P1, $C14$:P1, and $C15$:P1.
  • This setup ensures that the capacitors are in parallel, thereby increasing the overall capacitance and current handling capability.
• Grounding:
  • Ensure that all GND pins of related components are properly connected to a common ground plane to minimize noise and ensure stable operation.
    • Connect $C6$:P2, $C8$:P2, $C9$:P2, $C10$:P2, $C12$:P2, $C13$:P2, $C14$:P2, $C15$:P2 to GND.

1. Identify the ILIM Pin and Connection:
   • The ILIM pin on the BQ24075RGTT is connected as follows:
     • Connect U3:ILIM to R10:P1.
2. Determine Resistor Value:
   • The resistor R10 connected to ILIM is specified as 1kΩ.
3. Calculate the Current Limit:
   • The current limit calculation for the BQ24075RGTT can be found in its datasheet. Typically, the formula for the current limit is derived from: $I_{LIM} = \frac{V_{ILIM}}{R_{ILIM}}$ where $V_{ILIM}$ is defined in the datasheet, often with a reference voltage or a constant value specific to the IC.

4. Datasheet Parameters:
   • We will refer to the datasheet for the specific voltage used at the ILIM pin. Let’s assume a standard $ V_{ILIM} $ value given by the datasheet as 1V (please verify this from the actual datasheet).
5. Current Limit Calculation Execution: $I_{LIM} = \frac{1V}{1k\Omega} = 1mA$

• Verify $V_{ILIM}$ value from the BQ24075 datasheet (commonly it might be in the range of 100mV to 120mV).
• Use the exact formula found in the datasheet which might take into account additional constants or configurations.

1. Voltage ( $ V_{ILIM} $ ) specific to the BQ24075 for limiting current.
2. Any additional constants or multipliers applied to the formula.

• $V_{SET}$ is a constant voltage typically provided by the IC; according to the datasheet, $V_{SET}$ = 1V
• $R_{ISET}$ is the resistance connected to the ISET pin.

• Connect U3 to R4.
• Connect R4 to GND.

1. I2S Data In (DIN)
2. I2S Data Out (DOUT)
3. I2S Bit Clock (BCLK)
4. I2S Word Select (WS)

• I2S0 Data In (SD0): GPIO34
• I2S0 Data Out (SDI): GPIO35
• I2S0 Bit Clock (BCK): GPIO26
• I2S0 Word Select (WS): GPIO25

• GPIO25 (IO25): I2S0 Word Select (WS)
• GPIO26 (IO26): I2S0 Bit Clock (BCK)
• GPIO34 (IO34): I2S0 Data In (SD0)
• GPIO35 (IO35): I2S0 Data Out (SDI)

• Connect U1:IO25 to your I2S device WS pin
• Connect U1:IO26 to your I2S device BCK pin
• Connect U1:IO34 to your I2S device SD0 pin
• Connect U1:IO35 to your I2S device SDI pin

• $ V_{OUT} $ is the desired output voltage.
• $ R1 $ is R7.
• $ R2 $ is R6.

• $R7 = 165 \, k\Omega$
• $R6 = 100 \, k\Omega$

1. Resistor Values:
   • The values chosen for R6 and R7 are within the suggested range of 50kΩ to 100kΩ for good stability and noise performance[1].
2. Output Voltage:
   • The calculated output voltage of 3.29V is slightly above the common operational voltage of 3.3V but is acceptable considering typical tolerances.
3. Component Placement:
   • Ensure that the resistors are placed close to the feedback pin (U2) to minimize noise pickup[2].

• Adjust Tolerances: If precise output voltage is critical, consider using resistors with tighter tolerances or adjusting values slightly to achieve exactly 3.3V.
• Filter Network: If there is significant noise in the feedback loop, consider adding a small capacitor (e.g., 10pF) across R7 to filter high-frequency noise.

1. Capacitance Value:
   • The LM2623 datasheet should specify the recommended value for the bootstrap capacitor. Typically, a value between 10nF and 100nF is common.
   • In your design, you have not specified the value for the bootstrap capacitor connected to the BOOT pin. Ensure it falls within the recommended range mentioned in the datasheet.
2. Connection and Placement:
   • The bootstrap capacitor should be connected between the BOOT pin (pin 7) and the SW pin (pin 8).
   • Placement is critical. Place the bootstrap capacitor as close as possible to the BOOT and SW pins to minimize the effects of inductance and resistance, which can cause noise and inefficient switching.
3. Ripple Current Rating:
   • Ensure that the capacitor has a sufficient ripple current rating to handle the fast switching currents involved in the boost converter operation.
4. Low ESR and ESL:
   • Use a capacitor with low Equivalent Series Resistance (ESR) and Equivalent Series Inductance (ESL) to maintain efficiency and reduce noise.

• Net Name: Net 13
  • Members: U2:$$(BOOT)$$
• Net Name: Net 23
  • Members: $(PP3V3\_SW)$, U2:$$(SW)$$

• Connect $C11:$P1$ to U2:$$(BOOT)$$.
• Connect $C11:$P2$ to U2:$$(SW)$$.

• Ensure that the chosen capacitor maintains its capacitance value under the operating voltage conditions.
• Consider the voltage ratings and temperature coefficients. For instance, using X7R or X5R types provides better stability.

• Capacitor Value: Verify that $C11$ ($4.7pF$) is suitable for the bootstrap operation. Ensure it aligns with the typical bootstrap capacitor value range (usually higher than $4.7pF$).
• Synthesis: Given that $C11$ is a $4.7 pF$ capacitor as per the design, it might not suffice for a bootstrap capacitor. Consider replacing it with a $10nF$ to $100nF$ capacitor, such as a $100nF$, $10V$ rated ceramic capacitor.

1. Output Capacitance and Placement:
   • According to the design guidelines for the LM2623, it's crucial that the output capacitor is placed close to the regulator to minimize inductance and avoid voltage spikes $379caa0e-ae8a-5b1c-93ff-bc1d6f85ecc8$.
   • The typical application circuit for the LM2623 recommends a 100 µF tantalum capacitor for the output $d93fdc66-edce-56e0-9f6c-022052d29719$.
2. Current Configuration:
   • C13 with 22 µF capacitance
   • C12 with 22 µF capacitance
   • Both capacitors are on Net Net 13, providing a total output capacitance of 44 µF.

• Output Capacitance Value:
  • The provided output capacitance on Net Net 13 is 44 µF (combination of C13 and C12). This is below the 100 µF recommended value for typical applications.
• Potential Impact:
  • Insufficient output capacitance can lead to unstable output voltage and potential voltage spikes, which might compromise the reliability and performance of the circuit.
• Corrective Actions:
  • Increase the output capacitance closer to the recommended 100 µF. You can achieve this by:
    1. Adding additional capacitors in parallel to C13 and C12.
    2. Using a combination of different capacitor types (like tantalum and ceramic) to optimize performance.

1. Add an additional 56 µF capacitor:
   • Another capacitor like GRM21BR71A106KE51L to sum the total to approximately 100 µF.
2. Connections on Schematic:
   • Connect one additional 56 µF capacitor in parallel with C13 and C12.
     • Connect NewCap:1 to Net 13 (after connections to C13:P2 and C12:P2).
     • Connect NewCap:2 to GND.

1. Inductance Value: The inductor should have a value that is suitable for the switching frequency and the desired output ripple.
2. Saturation Current: The saturation current of the inductor must be higher than the peak current to avoid saturation.
3. DC Resistance (DCR): Lower DCR values will result in higher efficiency.
4. Current Rating: The heat rating current should be above the maximum output current to ensure safe operation.

• Desired Output Voltage ($V_{\text{out}}$): 3.3V
• Maximum Output Current ($I_{\text{max}}$): 500mA
• Inductor Model: YSPI1365-470M
• Inductor Specification:
  • Inductance: 47 μH
  • DC Resistance (DCR): 0.12 Ω
  • Heat Rating Current: 2.6A
  • Saturation Current: 3.55A

1. Inductance Value:
   • The inductor value of 47μH is reasonable for the LM2623 based on its typical application.
2. Peak Current Calculation:
   • The peak current in the inductor can be calculated using the following formula:
     $$I_{\text{peak}} = I_{\text{out}} + \frac{\Delta I}{2}$$
     where $ \Delta I $ is the ripple current. Ripple current ($ \Delta I $) can be estimated as:
     $$\Delta I = \frac{V_{\text{out}} (1 - D)}{L \cdot f}$$
     For a rough estimate, assuming duty cycle $ D = 0.5 $ and $ f = 1MHz $:
     $$\Delta I = \frac{3.3V \times 0.5}{47\muH \times 1MHz} \approx 0.035A$$
     Thus, the peak current:
     $$I_{\text{peak}} = 0.5A + \frac{0.035A}{2} \approx 0.5175A$$
3. Check Saturation Current:
   • The saturation current of the inductor is 3.55A, which is well above the peak current of 0.5175A. Hence, it's acceptable.
4. Heat Rating Current:
   • The inductor's heat rating current is 2.6A, which is significantly higher than the maximum output current of 500mA. This implies it should operate without significant temperature rise.

• Connect L1:P1 to U2:SW.
• Connect L1:P2 to D1:A.

1. CLK (clock) connection:
   • Connect $U4:CLK$ to $U1:GPIO14$.
2. CMD (command) connection:
   • Connect $U4:CMD$ to $U1:GPIO15$.
3. DAT0 (data line 0) connection:
   • Connect $U4:DAT0$ to $U1:GPIO2$.
4. DAT1 (data line 1) connection:
   • Connect $U4:DAT1$ to $U1:GPIO4$.
5. DAT2 (data line 2) connection:
   • Connect $U4:DAT2$ to $U1:GPIO12$.
6. DAT3 (data line 3) connection:
   • Connect $U4:CD/DAT3$ to $U1:GPIO13$.
7. Power connections:
   • Connect $U4:VDD$ to a 3.3V power supply, e.g., $PP3V3:P1$.
   • Connect $U4:GND_1$, $U4:GND_2$, $U4:GND_3$, $U4:GND_4$, and $U4:VSS$ to GND.

• Connect $U4:CLK$ to $U1:GPIO14$.
• Connect $U4:CMD$ to $U1:GPIO15$.
• Connect $U4:DAT0$ to $U1:GPIO2$.
• Connect $U4:DAT1$ to $U1:GPIO4$.
• Connect $U4:DAT2$ to $U1:GPIO12$.
• Connect $U4:CD/DAT3$ to $U1:GPIO13$.
• Connect $U4:VDD$ to $PP3V3:P1$.
• Connect $U4:GND_1$, $U4:GND_2$, $U4:GND_3$, $U4:GND_4$, and $U4:VSS$ to GND.

1. CLK (clock) connection:
   • Connect $U4:CLK$ to $U1:GPIO5$.
2. CMD (command) connection:
   • Connect $U4:CMD$ to $U1:GPIO6$.
3. DAT0 (data line 0) connection:
   • Connect $U4:DAT0$ to $U1:GPIO7$.
4. DAT1 (data line 1) connection:
   • Connect $U4:DAT1$ to $U1:GPIO8$.
5. DAT2 (data line 2) connection:
   • Connect $U4:DAT2$ to $U1:GPIO9$.
6. DAT3 (data line 3) connection:
   • Connect $U4:CD/DAT3$ to $U1:GPIO10$.
7. Power connections:
   • Connect $U4:VDD$ to a 3.3V power supply, e.g., $PP3V3:P1$.
   • Connect $U4:GND_1$, $U4:GND_2$, $U4:GND_3$, $U4:GND_4$, and $U4:VSS$ to GND.

• Connect $U4:CLK$ to $U1:GPIO5$.
• Connect $U4:CMD$ to $U1:GPIO6$.
• Connect $U4:DAT0$ to $U1:GPIO7$.
• Connect $U4:DAT1$ to $U1:GPIO8$.
• Connect $U4:DAT2$ to $U1:GPIO9$.
• Connect $U4:CD/DAT3$ to $U1:GPIO10$.
• Connect $U4:VDD$ to $PP3V3:P1$.
• Connect $U4:GND_1$, $U4:GND_2$, $U4:GND_3$, $U4:GND_4$, and $U4:VSS$ to GND.

1. Input Capacitor (C1): Typically 10 uF.
2. Output Capacitor (C2): Typically a 100 uF tantalum capacitor. The exact part you might consider is a C1206X106J4RACAUTO.
3. Inductor (L1): Typically around 10 µH to 22 µH, rated for the input and output currents.
4. Schottky Diode (D1): Suitable for the voltage and current levels, such as an SS34.
5. Feedback Resistors (R1, R2): These will set your output voltage. Let's choose standard values like 100k ohms for RF2.
6. Frequency Set Resistor (R3): To set the operating frequency. This could vary based on your desired frequency, often something like 100k ohms.

• Input Capacitor (C1): 10 µF (S1V, low ESR electrolytic)
• Output Capacitor (C2): 100 µF tantalum capacitor
• Inductor (L1): 10 µH to 22 µH, e.g., part like 7447709100 (Wurth)
• Schottky Diode (D1): e.g., SS34 (40V, 3A)
• Feedback Resistors (R1, R2): R1 to 100k ohms (RF2 in the detailed design)
• Frequency Set Resistor (R3): 100 k ohms

1. Input Capacitor:
   • Connect positive terminal to VIN.
   • Connect negative terminal to GND.
2. Output Capacitor:
   • Connect positive terminal to VOUT.
   • Connect negative terminal to GND.
3. Inductor:
   • Connect one end to SW pin.
   • Connect the other end to the cathode of the Schottky diode (D1).
4. Schottky Diode:
   • Connect cathode (negative) to the other side of the inductor.
   • Connect anode (positive) to GND.
5. Feedback Resistors:
   • Connect R1 between VOUT and FB pin.
   • Connect R2 between FB pin and GND.
6. Frequency Set Resistor:
   • Connect R3 between FREQ pin and GND.

• Connect C1:P1 to VIN.
• Connect C1:P2 to GND.
• Connect C2:P1 to VOUT.
• Connect C2:P2 to GND.
• Connect L1 to SW pin of U2.
• Connect L1 to cathode of D1.
• Connect, Anode of D1 to GND.
• Connect R1 between VOUT and FB pin.
• Connect RF2 between FB pin and GND.
• Connect R3 between FREQ pin and GND.

1. Feedback Resistive Divider (RF1 and RF2):
   • The output voltage is set using the resistive divider formed by RF1 and RF2 based on the formula:
     $ RF1 = RF2 \times \left(\frac{V_{OUT}}{1.24} - 1\right) $
   • Here, $V_{OUT} = 3.3,V$.
   • Let’s choose a value for RF2 within the recommended range of 50k to 100k. Let's use $ RF2 = 100 k\Omega $.
   • Now calculate RF1:
     $ RF1 = 100 k\Omega \times \left(\frac{3.3}{1.24} - 1\right) $ $ RF1 \approx 166 k\Omega $
2. Capacitors:
   • Input Capacitor (C1):
     • Choose a ceramic capacitor with a value of 10µF, 6.3V or higher.
   • Output Capacitor (C2):
     • Choose a tantalum or ceramic capacitor with a value of 100µF, 10V or higher.
3. Inductor:
   • Choose an inductor with a value of around 10µH to 47µH. Let's assume a 22µH inductor is usually a good choice.
4. VDD Supply:
   • The VDD supply must be between 3V to 5V[1].

• Connect R1 with a value of 166kΩ and R2 with a value of 100kΩ as follows:
  • Connect R1:1 to U2:FB.
  • Connect R2:1 to U2:FB and U2:SGND.
• Input Capacitor:
  • Connect C1:1 to your power supply (around 1.1V to 3V).
  • Connect C1:2 to U2:PGND.
• Output Capacitor:
  • Connect C2:1 to U2:SW.
  • Connect C2:2 to U2:PGND.
• Inductor:
  • Connect one side of the inductor to U2:VDD.
  • Connect the other side to the SW pin of U2.

1. Inductor:
   • For efficient step-up conversion, you typically use inductance values in the range of $4.7\mu H$ to $22\mu H$. A value of $10\mu H$ is often recommended for moderate current loads while ensuring a compact size.
     • Recommended inductor value: $4.7\mu H$ to $10\mu H$
2. Output Capacitor (C2):
   • The output capacitor should be chosen to minimize output ripple and maintain stability. A $47\mu F$ ceramic capacitor should be sufficient in this context, balancing size and performance.
     • Recommended capacitor value: $47\mu F$, $6.3V$ or higher

• Inductor ($10\mu H$):
  • Choose an inductor with appropriate current rating. Given the input and output characteristics, a $10\mu H$ inductor should be sufficient.
• Capacitors:
  • Input Capacitor (C1): $10\mu F$ ceramic, $6.3V$ or higher
  • Output Capacitor (C2): $47\mu F$ ceramic, $6.3V$ or higher

1. Feedback Resistive Divider:
   • Connect R1:1 ($166k\Omega$) to U2:FB.
   • Connect R1:2 to U2:Vout.
   • Connect R2 ($100k\Omega$) between U2:FB and U2:SGND.
2. Capacitors:
   • Connect C1:1 to VIN (e.g. $2.8V$ to $3.7V$ supply) and C1:2 to U2:PGND.
   • Connect C2:1 to VOUT ($3.3V$ output) and C2:2 to U2:PGND.
3. Inductor:
   • Connect one side of the inductor to VIN (e.g. $2.8V$ to $3.7V$ supply).
   • Connect the other side of the inductor to U2:SW.

1. Connect [R1]:1 ($166k\Omega$) to U2:FB.
2. Connect [R1]:2 to U2:Vout.
3. Connect [R2]:1 ($100k\Omega$) to U2:FB.
4. Connect [R2]:2 to U2:SGND.
5. Connect [C1]:1 ($10\mu F$, input) to VIN ($2.8V$ to $3.7V$ supply).
6. Connect [C1]:2 ($10\mu F$) to U2:PGND.
7. Connect [C2]:1 ($47\mu F$, output) to VOUT ($3.3V$ output).
8. Connect [C2]:2 ($47\mu F$) to U2:PGND.
9. Connect the inductor between VIN ($2.8V$ to $3.7V$ supply) and U2:SW.

• Forward Voltage: Low (to reduce power loss)
• Current Rating: Adequate to handle the peak current of the boost converter
• Reverse Voltage: Greater than 3.3V (e.g., 20V or more for some headroom)

• Forward Voltage ($V_f$): 0.36V at 1A
• Maximum Average Rectified Current ($I_f$): 1A
• Reverse Voltage ($V_r$): 20V
• Package: SOD-123FL

• Anode: Connect to U2:SW
• Cathode: Connect to the output capacitor and the Vout

• Connect MBR120VLSFT3G:Anode to U2:SW.
• Connect MBR120VLSFT3G:Cathode to the positive terminal of the output capacitor and Vout.

• Forward Voltage ($V_f$): 0.45V at 2A
• Maximum Average Rectified Current ($I_f$): 2A
• Reverse Voltage ($V_r$): 40V
• Package: SOD-123FL

• Anode: Connect to U2:SW
• Cathode: Connect to the output capacitor and the Vout

• Connect SS24FL:Anode to U2:SW.
• Connect SS24FL:Cathode to the positive terminal of the output capacitor and Vout.

1. Configuring Operating Modes or Strapping Pins:
   • In some designs, a resistor like $R3$ is used to set the initial state of pins that determine the operating mode or boot configuration of the microcontroller. These are often known as "strapping pins."
   • According to the ESP32-S3 datasheet, strapping pins require pull-up or pull-down resistors to define the initial states at power-up.
2. Pull-up/Pull-down on Control or Enable Pins:
   • Another common usage is on enable (EN) pins or similar control pins, ensuring they are in a known state during power-up. For example, ensuring a pin is pulled high to enable a module, or pulled low to disable it by default.

• In this case, $R3$ could be connected to a pin like the EN (Enable) pin of the ESP32-S3 to ensure it is pulled to the expected logic level during startup. If it is a pull-up resistor, it ensures the EN pin is high, enabling the chip.

• If $R3$ is acting as a pull-up resistor for the EN pin:
  • Connect one side of $R3$ to the EN pin ($U1$:EN)
  • Connect the other side of $R3$ to the supply voltage (VCC or 3.3V).

1. Voltage Drop Across Resistor: $V_{R} = I \cdot R = 1 \, \text{A} \times 1000 \, \Omega = 1000 \, \text{V}$

2. Voltage Drop in more Practical Context: $V_{R} = 0.001 \, \text{A} \times 1000 \, \Omega = 1 \, \text{V}$
3. Power Dissipation: $P = I^2 \cdot R = (0.001 \, \text{A})^2 \cdot 1000 \, \Omega = 1 \, \text{mW}$

• Practical Power Rating: $2 \times 1 \, \text{mW} = 2 \, \text{mW}$

• Smallest Standard Power Rating: 1/8 Watt (125 mW)

1. Input Capacitor: A capacitor (typically 10uF) between the input pin (IN) and ground (GND) to filter out noise.
   • Connect C7:P2 to GND.
   • Connect C7:P1 to U3:IN.
2. Output Capacitors: At least one capacitor (usually around 10uF) between the output pins (OUT_1, OUT_2) and ground.
   • Connect C8:P1 to GND.
   • Connect C8:P2 to U3:OUT_1 and OUT_2.
3. Battery Connection: Connect the battery to the BAT pins.
   • Connect the positive terminal of the battery to U3:BAT_1 and BAT_2 via the battery connector.
   • Connect the negative terminal of the battery to GND.
4. Thermistor: For temperature monitoring, connect a thermistor between the TS pin and ground.
   • Connect one end of the thermistor to U3:TS.
   • Connect the other end of the thermistor to ground.
5. Charge Current Set Resistor: A resistor (typically 1k-10k) to set the charge current.
   • Connect one end of the resistor to U3:ISET.
   • Connect the other end of the resistor to ground.
6. Timer Capacitor: A small capacitor (usually 0.1uF) connected to the TMR pin for setting the charge time.
   • Connect one end of the capacitor to U3:TMR.
   • Connect the other end of the capacitor to ground.

• Thermistor:
  • Connect THERMISTOR:P1 to THERM_P:P1.
  • Connect THERMISTOR:P2 to THERM_N:P1.
  • Connect THERM_N:P1 to U3:TS.
• Resistor for ISET: You need a resistor to define the charging current:
  • Connect one end of the resistor to U3:ISET.
  • Connect the other end to GND.
• Capacitor for TMR:
  • Connect one end of the capacitor to U3:TMR.
  • Connect the other end to GND.

• $I_{CHG}$ is the desired charge current in Amperes.
• $V_{ISET}$ is a reference voltage, typically provided in the datasheet. For the BQ24075RGTT, it's usually 1V.
• $R_{ISET}$ is the resistance of the ISET resistor in Ohms.

• Desired charge current, $I_{CHG} = 1 ; A$

1. Identify Reference Voltage: $ V_{ISET} $ is typically 1V (Refer to datasheet for confirmation).
2. Rearrange the Formula to Solve for Resistor Value: $ R_{ISET} = \frac{V_{ISET}}{I_{CHG}} \times 1000 $
3. Substitute the Values: $ R_{ISET} = \frac{1V}{1A} \times 1000 $ $ R_{ISET} = 1 \Omega \times 1000 $ $ R_{ISET} = 1000 \Omega $

• For a charge current of 1A, you will need a 1kΩ resistor for ISET.

• For a different desired charge current, say $I_{CHG,x}$, the general formula becomes: $ R_{ISET} = \frac{1V}{I_{CHG,x}} \times 1000 $

• Suppose you want a charge current of 0.5A: $ R_{ISET} = \frac{1V}{0.5A} \times 1000 $ $ R_{ISET} = 2k \Omega $

• Let's assume we want a 3-hour termination time.

• $ T_{TERM} $ is the desired termination time in hours.
• $ C_{TMR} $ is the value of the timer capacitor in Farads.

1. Rearrange the formula to solve for $ C_{TMR} $: $C_{TMR} = \frac{T_{TERM}}{2.5 \times 10^3}$
2. Substitute the values: $C_{TMR} = \frac{3}{2.5 \times 10^3}$ $C_{TMR} = \frac{3}{2500} \; (Farads)$ $C_{TMR} = 1.2 \times 10^{-3} \; (Farads)$ $C_{TMR} = 1.2 \mu F$

• For a 3-hour termination time, you will need a 1.2 $\mu$F capacitor for the timer.

• Desired termination time, $T_{TERM} = 1.5 ; \text{hours}$

1. Rearrange the formula to solve for $C_{TMR}$: $C_{TMR} = \frac{T_{TERM}}{2.5 \times 10^3}$
2. Substitute the values: $C_{TMR} = \frac{1.5 \; \text{hours}}{2.5 \times 10^3}$ $C_{TMR} = \frac{1.5}{2500} \; \text{Farads}$ $C_{TMR} = 6 \times 10^{-4} \; \text{Farads}$ $C_{TMR} = 600 \; \text{nF}$

• For a 1.5-hour termination time, you will need a 600 nF capacitor for the timer.