ESP32 Power and Power Management: Hardware Design for Power Optimization

The power optimization hardware design for the ESP32 is the cornerstone of achieving ultra-low power systems, requiring meticulous control over power architecture, peripheral circuits, PCB layout, and more. Below are hardware-level optimization solutions validated by engineering:

1. Power Topology Optimization

1. Efficient Power Conversion Solutions

Scenario	Recommended Solution	Static Current	Conversion Efficiency	Key Models
Input Voltage >3.8V (Lithium Battery)	Synchronous Rectification Buck DC-DC	1-15 μA	>95%	TI TPS62740, MPS MP2615
Input Voltage 2.7~4.2V	Ultra-Low Static Current LDO	0.6-1 μA	70~85%	TI TPS70933, ADM7150
Button Battery Power Supply (2-3V)	Hysteresis Boost Converter	0.5 μA	>80%	TPS61222, MAX17222

Design Key Points:

For lithium battery power supply, choose a DC-DC + LDO two-stage architecture: DC-DC handles high step-down ratios, and LDO performs post-stage filtering

For button battery systems, disable the DC-DC switch (cut off with the EN pin), keeping only the pulse mode of the hysteresis boost

2. Key Circuit Module Design

1. Power Switch Circuit

                        ┌───────────┐
  VBAT ────┬─────►│ EN       │
          │      │  TPS22810 │─────► VCC_ESP (3.3V)
      ┌───┴───┐   │          │
      │ 100kΩ │   └───────────┘
      └───┬───┘           ▲
          ▼               │
      ┌──────┐        ┌──────┐
      │ MOSFET│◄───────┤ ESP32│
      │(Si2302)       │ GPIO │
      └──────┘        └──────┘

Function completely cuts off the power circuit of the ESP32 and peripherals, eliminating μA level leakage current
Selection Requirements

MOSFET: Leakage current <1nA (e.g., Si2302)
Load Switch: On-resistance <50mΩ (e.g., TPS22810)

2. Low Power Sensor Interface

// Dynamic control of sensor power
#define SENSOR_PWR_GPIO GPIO_NUM_15

void read_sensor() {
  gpio_set_level(SENSOR_PWR_GPIO, 1);  // Power on
  vTaskDelay(50 / portTICK_PERIOD_MS); // Wait for stabilization
  // Read sensor data...
  gpio_set_level(SENSOR_PWR_GPIO, 0);  // Power off immediately
}

Power Saving Effect when off, the sensor leakage current approaches 0

3. PCB Layout Golden Rules

1. Power Layer Design

4-layer board structure<span>TOP (Signal) ── GND ── 3.3V_PWR ── BOTTOM (Signal)</span>
Key Measures

Power plane avoid segmentation, reduce impedance
Place 10μF MLCC + 0.1μF ceramic capacitor next to the VDD pin of the ESP32 (distance <2mm)

2. High Interference Signal Isolation

           ┌───────────────┐
           │   ESP32       │
           │               │
    RF Antenna ─┤ANT     EN     ├─► Shield Ground
           │               │     │
DC-DC Noise Zone┼┤VIN     VDD   ├─┼─── 3cm spacing
           │               │     │
Sensor Interface ─┤GPIO15   ADC   ├─► π-type Filter
           └───────────────┘

Wiring Principles

WiFi/BT RF traces 50Ω impedance control, away from DC-DC and crystal oscillators
Analog signals (ADC, DAC, touch) should be wrapped with guard rings

4. Component Selection Black Technology

1. Passive Components

Type	Optimization Direction	Recommended Model/Parameters	Power Saving Effect
Capacitor	Low ESR + High Capacitance	TDK C3225X7R1H106K	Reduce power ripple by 60%
Ferrite Bead	High-frequency noise suppression	Murata BLM18PG121SN1	Reduce RF interference power consumption
Crystal Oscillator	Low power active crystal oscillator	EPSON SG-8101	Save 20μA in standby

2. Battery Interface Protection

 Lithium + ────►│ P+       P- │◄─── Load
            │             │
            │ BQ27621     │
 Lithium - ────►│ S-       S+ │◄─── GND
            └─┬───────┬──┘
              │       │
           100Ω     4.7kΩ
              │       │
            TS      BAT_DET (to ESP32 ADC)

Function accurately monitors battery level + over-discharge protection
Solution Coulomb counter chip (e.g., TI BQ27621), power consumption only 45μA

5. Real-World Power Consumption Comparison

Optimization Measures	Button Battery System (CR2032)	Lithium Battery System (1000mAh)
Basic Design (Unoptimized)	Standby 150μA → 2 months of battery life	Standby 50μA → 8 months of battery life
DC-DC + LDO Two-Stage Power Supply	Standby 25μA	Standby 15μA
MOSFET Full Power Cut Control	<1μA	<1μA
Dynamic Sensor Switching	Measurement +180μA	Measurement +200μA
Final Battery Life Improvement	5 years → 10 years↑	8 months → 5 years↑

6. Pitfall Guide: Fatal Hardware Traps

GPIO Leakage Current

Phenomenon Deep Sleep still has >5μA current
Countermeasure Configure all unused GPIOs as input mode + disconnect external pull-up/pull-down
```
gpio_reset_pin(GPIO_NUM_X); 
gpio_set_direction(GPIO_NUM_X, GPIO_MODE_INPUT);
```

Incorrect LDO Selection

Case Choosing AMS1117 (static current 5mA) caused the button battery to deplete in a few days
Solution Switch to TPS709xx (static current 1μA)

PCB Parasitic Leakage

Detection Method Apply insulating nano-coating (e.g., HumiSeal 1B73)
Effect Leakage current in humid environments reduced from >50μA to <5μA

Ultimate Optimization Combination

Power Path Lithium battery → TPS62740 (93% efficiency) → TPS70933 (1μA IQ) → ESP32
Wake-Up Scheme ULP co-processor + touch sensor (wakes main CPU every 1 hour)
Communication Protocol ESP-NOW point-to-point transmission (saves 70% more energy than Wi-Fi)

Design Maxim: Hardware power saving is a battlefield of “microamps must be fought for” —“Converters as quiet as snow, power switches as fast as knives, PCB traces as clean as water, leakage has nowhere to escape”