Explore in-depth circuit information and repair tips for the Boat Stone 350 Bluetooth speaker. Ensure optimal performance with our detailed resources.
The Boat Stone 350 is a compact yet powerful Bluetooth speaker that incorporates various ICs and components for audio generation, amplification, and power management. Below is a step-by-step explanation of the circuit, focusing on each critical component and its role.
1. Main IC: JL AC6969 - 25C4 Series IC
Bluetooth IC Details:
IC Number: AS20BP01888-25C4
IC others Number: JL6969-25C4 Series
Pin Count: 24
Functionality: Acts as the main CPU responsible for Bluetooth functionality, audio decoding, and signal processing.
Connections:
Input Section:
The IC connects directly to the audio source via Bluetooth or auxiliary input.
Decodes the audio signals into left and right channels for further amplification.
Control Signals:
Sends power management and control signals to other ICs, such as the audio amplifier and charging IC.
Crystal Oscillator:
Works with the 24 MHz crystal to maintain the IC's operational clock frequency for precise Bluetooth communication and processing.
Power Supply:
Powered by a boosted voltage from the power management circuit (PVOUT of the amplifier IC).
Requires stable input voltage; decoupling capacitors (C3, C11) suppress noise.
2. Audio Amplifier IC: FT2925P
IC Details:
Amplifier IC Number: FT2925P
IC Pin Count: 28
Functionality: Stereo audio amplifier driving left and right speakers in a Bridge-Tied Load (BTL) configuration.
Boost Regulator: Includes an internal boost converter to step up the supply voltage for higher power output to the speakers.
Connections:
Input Pins (INPL, INNL, INPR, INNR):
Receives decoded left and right audio signals from the JL6969 series IC.
AC coupling capacitors block any DC components.
Output Pins (VOPL/VONL, VOPR/VONR):
Outputs amplified signals to the left and right speakers.
Drives 4Ω or 8Ω speakers with higher efficiency due to the BTL configuration.
Boost Circuit:
LX (Pins 15, 16) connects to the boost inductor (3R3).
PVOUT stabilizes the boosted voltage with low-ESR capacitors (10 µF, C13, C17, C20).
Schottky diode (SS34) prevents reverse current during switching.
3. Crystal Oscillator
Crystal Details:
Frequency: 24 MHz
Functionality: Provides a precise clock signal for the main IC (JL6969 series).
Connections:
Connected to the JL6969 series IC via pins Y1 and adjacent ground.
Ensures stable Bluetooth communication and system timing.
4. Power Management and Charging Section
Charging IC:
The unidentified 8-pin IC is responsible for managing battery charging via the Micro-B USB port.
Likely includes functions such as overcurrent protection, fast charging, and battery status indication.
Charging Port:
Type: Micro-B USB.
Supplies input voltage (typically 5V) for battery charging.
Boost Coil:
Specification: 3R3 (3.3 µH).
Functionality: Works with the FT2925P to step up the supply voltage for the amplifier and speakers.
Capacitors:
Three 10V, 470 µF electrolytic capacitors for decoupling and energy storage, ensuring stable power supply during high current draw.
5. Audio Output Section
Speakers:
Left and right speakers are connected directly to the amplifier output pins (VOPL/VONL, VOPR/VONR).
Operate in BTL mode, doubling the voltage swing across the load and eliminating the need for coupling capacitors.
Performance:
Efficient power delivery due to the internal boost converter.
Clear audio output with minimal distortion, ideal for portable applications.
6. Circuit Flow
Power Input:
5V is supplied through the Micro-B USB port to the charging IC, which charges the internal Li-ion battery.
Boosted voltage is generated by the FT2925P's boost regulator, powering the main IC and amplifier.
Bluetooth Connectivity:
The JL6969 series IC pairs with the audio source via Bluetooth.
Decodes the audio signal into left and right channels.
Signal Amplification:
Audio signals are fed to the FT2925P for amplification.
The amplified signals are sent to the speakers for audio output.
Speaker Output:
High-power audio is delivered to the speakers in stereo, ensuring a rich sound experience.
7. Troubleshooting Tips
No Power:
Check the charging IC and ensure proper voltage at the Micro-B port.
Distorted Audio:
Verify the boost inductor (3R3) and capacitors (C13, C17, C20) for faults.
No Bluetooth Connection:
Check the crystal oscillator (24 MHz) for damage.