You are a Senior Embedded Hardware Design Engineer specializing in compact consumer electronics and portable audio systems.

OBJECTIVE

Design Version V1 of a compact audio switching and amplification platform for a highlighter-shaped portable audio device.

The objective is to verify the electrical architecture before PCB development.

The design should prioritize:

• Small size
• Low power consumption
• Low audio noise
• High audio quality
• Minimal component count
• SMD components wherever possible
• Easy future PCB integration

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AVAILABLE MODULES

Bluetooth Audio Module

Pins available:

B+
B-
L+
L-
R+
R-
Power Button
Volume+
Volume-

The Bluetooth module is already experimentally verified to work with a PAM8403 amplifier.

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DFPlayer Mini

Use ONLY

DAC_L
DAC_R

Do NOT use

SPK1
SPK2

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POWER

3.7V Li-ion Battery

Battery Charging Module

Battery Protection

Required voltage regulation if necessary.

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SYSTEM REQUIREMENTS

Only ONE audio source can play at a time.

Priority:

Bluetooth Connected

↓

Bluetooth Audio

Bluetooth Disconnected

↓

DFPlayer Audio

No simultaneous playback.

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OUTPUT MODES

Two audio modes are required.

Mode 1

Normal

Low power

Personal listening

Low speaker volume

Mode 2

Amplified

High speaker volume

External amplifier enabled

The same speaker shall be used in both modes.

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MODE CONTROL

One push button.

Each press toggles

Normal

↓

Amplified

↓

Normal

↓

Amplified

State must be remembered electronically.

Do not use ESP32.

Do not use Arduino.

Use small logic ICs.

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SOURCE SWITCHING

Design automatic switching between

Bluetooth

and

DFPlayer.

Use analog switches, multiplexers, MOSFETs or other suitable integrated circuits.

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AMPLIFIER

Recommend a better amplifier than PAM8403.

Prioritize

Low THD

Low Noise

Battery Operation

Small Size

High Efficiency

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OUTPUT

Provide

1. Complete schematic

2. Complete connection list

3. Component list

4. IC recommendations

5. Power routing

6. Audio routing

7. Logic routing

8. Button routing

9. Suggested resistor values

10. Suggested capacitor values

11. Decoupling capacitors

12. Filtering components

13. Noise reduction methods

14. Grounding strategy

15. Simulation procedure

16. Test sequence

17. Expected voltages

18. Possible failure points

19. Improvements for Version V2

Do not simplify the design.

Assume this will become a real consumer product.