Single-Chip Microcontroller Lithium Battery Power Management & Voltage Detection

 For battery-powered embedded systems (e.g., IoT devices, wearables), efficient power management and voltage monitoring are critical. Below is a comprehensive guide to implementing Li-ion/LiPo battery power and voltage detection using a single microcontroller (e.g., STM32, ESP32, PIC).

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1. Power Supply Options for Li-ion/LiPo Batteries

Method	Pros	Cons
Direct Connection	Simple, no extra components	Risk of undervoltage damage
LDO Regulator	Stable 3.3V/5V output	Inefficient (high dropout voltage)
Buck-Boost Converter	High efficiency (e.g., TPS63020)	Complex circuit
PMIC ICs	Integrated charging/protection	Higher cost (e.g., MAX1555)

Typical Setup:

Li-ion Battery (3.7V) → Buck-Boost Converter → 3.3V MCU  
                      └─ Voltage Divider → ADC (for monitoring)

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2. Voltage Detection Using MCU ADC

Hardware Design

1. Voltage Divider (for safe ADC input):

   • Li-ion range: 3.0V–4.2V → Scale to MCU ADC range (e.g., 0–3.3V).

   • Example: Use R1=100kΩ, R2=200kΩ → V_adc = V_bat / 3.

2. ADC Configuration:

   • 12-bit ADC (common in STM32/ESP32) → Resolution: 3.3V / 4096 ≈ 0.8mV.

   • Enable internal voltage reference (if available) for accuracy.

Software Implementation (STM32 HAL Example)

c

// Configure ADC
ADC_HandleTypeDef hadc;
hadc.Instance = ADC1;
hadc.Init.Resolution = ADC_RESOLUTION_12B;
HAL_ADC_Init(&hadc);

// Read battery voltage
float Read_Battery_Voltage() {
  HAL_ADC_Start(&hadc);
  uint32_t adc_val = HAL_ADC_GetValue(&hadc);
  float v_adc = adc_val * 3.3f / 4095;  // Convert to voltage
  float v_bat = v_adc * 3.0f;           // Account for voltage divider (R1=100k, R2=200k)
  return v_bat;
}

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3. Low-Battery Detection & Safety

Undervoltage Protection

• Hardware: Use a voltage supervisor IC (e.g., TLV809, MAX809).

• Software: Poll ADC and enter sleep/shutdown if V_bat < 3.3V.

c

if (Read_Battery_Voltage() < 3.3) {
  Enter_Low_Power_Mode();  // Halt or sleep MCU
}

Overvoltage Protection

• Required if using USB charging.

• Use a protection IC (e.g., DW01A + FS8205 for Li-ion).

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4. Power Efficiency Optimization

Technique	Description
Sleep Modes	Use STOP or STANDBY mode in STM32.
Dynamic Clock Scaling	Reduce clock speed when idle (e.g., PLL off).
Peripheral Management	Disable unused peripherals (__HAL_RCC_GPIOA_CLK_DISABLE()).
ADC Sampling Rate	Lower sample rate for infrequent monitoring.

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5. Battery Charging (Optional)

For rechargeable systems:

• TP4056 (1A linear charger, simple).

• BQ25601 (I²C programmable, with power path).

Wiring Example:

USB 5V → TP4056 → Li-ion Battery → Buck Converter → MCU  

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6. Real-World Applications

1. Wireless Sensors (ESP32 + LiPo, ADC monitoring).

2. Portable Medical Devices (STM32L4 + buck-boost).

3. Drones (Voltage detection for flight time estimation).

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7. Recommended Components

Component	Example Part	Purpose
Buck-Boost Converter	TPS63020	Efficient 3.3V regulation
Voltage Divider	100kΩ + 200kΩ resistors	Safe ADC input scaling
Protection IC	DW01A + FS8205	Overcharge/discharge protection
Charger IC	TP4056	Simple Li-ion charging

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Conclusion

A single-chip MCU can efficiently manage Li-ion battery power with:
✔ ADC-based voltage monitoring (scaled via voltage divider).
✔ Low-power modes to extend battery life.
✔ Optional charging/protection circuits for robustness.