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Espressif Systems ESP32 Hardware Design Manuallines

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ESP32 Hardware Design Guidelines
Version 2.1
Espressif Systems

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Summary of Contents for Espressif Systems ESP32

  • Page 1 ESP32 Hardware Design Guidelines Version 2.1 Espressif Systems...
  • Page 2 About This Guide The guidelines outline recommended design practices when developing standalone or add-on systems based on the ESP32 series of products, including ESP32, the ESP32-WROOM-32(ESP-WROOM-32) module, and ESP32- DevKitC — the development board. About This Guide This document provides the specifications of ESP32 hardware.

  • Page 3: Table Of Contents

    2.2.3.2 Q: The power ripple is small, but RF Tx performance is poor. 2.2.3.3 Q: When ESP32 sends data packages, the power value is much higher or lower than the target power value, and the EVM is relatively poor. 2.2.3.4 Q: Tx performance is not bad, but the Rx sensitivity is low.
  • Page 4 ESP-WROVER-KIT Development Board 4 Applications UART to Wi-Fi Smart Device ESP32-PICO-KIT Mini Development Kit ESP32-LyraT Smart Audio Platform...
  • Page 5 List of Tables Pin Definition of UART Interfaces...
  • Page 6 ESP32 External Capacitor ESP32 UART ESP32 PCB Layout ESP32 Module Antenna Position on Base Board Keepout Zone for ESP32 Module’s Antenna on the Base Board ESP32 Power Supply Design ESP32 Crystal Oscillator Layout ESP32 RF Layout A Typical Touch Sensor Application...

  • Page 7: Overview

    1. OVERVIEW 1. Overview ESP32 is a single 2.4 GHz Wi-Fi and Bluetooth combo chip designed with TSMC ultra-low-power 40 nm technol- ogy. It is designed to achieve the best power and RF performance, robustness, versatility, and reliability in a wide variety of applications and different power profiles.

  • Page 8: Schematic Checklist And Pcb Layout Design

    2. SCHEMATIC CHECKLIST AND PCB LAYOUT DESIGN 2. Schematic Checklist and PCB Layout Design ESP32’s integrated circuitry requires only 20 resistors, capacitors and inductors, one crystal and one SPI flash memory chip. ESP32 integrates the complete transmit/receive RF functionality including the antenna switches, RF balun, power amplifier, low noise receive amplifier, filters, power management module, and advanced calibration circuitries.

  • Page 9: Power Supply

    Pin1, Pin43 and Pin46 are the analog power supply pins. Pin3 and Pin4 are the power supply pins for the power amplifiers. It should be noted that the sudden increase in current draw, when ESP32 is in transmission mode, may Espressif Systems ESP32 Hardware Design Guidelines V2.1...

  • Page 10: Power-On Sequence And System Reset

    2.1.2.1 Power-on Sequence ESP32 uses a 3.3V system power supply. The chip should be activated after the power rails have stabilized. This is achieved by delaying the activation of CHIP_PU (Pin9) by time T after the 3.3V rails have been brought up. The rec- ommended delay time (T) is given by the parameter of the RC(R = 10 kΩ, C = 0.1 µF) circuit.

  • Page 11: Reset

    2.1.2.2 Reset CHIP_PU serves as the reset pin of ESP32. ESP32 will reset when CHIP_PU is held low and the input level is below 0.6V and stays for at least 200 µs. To avoid reboots caused by external interferences, the CHIP_PU trace should be as short as possible and routed away from the clock lines.

  • Page 12: Esp32 Crystal Oscillator

    Figure 5: ESP32 Crystal Oscillator Notice: Defects in the craftsmanship of the crystal oscillators (for example, high frequency deviation) and unsta- ble operating temperature may lead to the malfunction of ESP32, resulting in a decrease of the overall performance. Espressif Systems...

  • Page 13: Rtc (Optional)

    If the RTC source is not required, then Pin12 32K_XP and Pin13 32K_XN can be used as GPIOs. 2.1.5 RF The output impedance of the RF pins of ESP32 (QFN 6*6) and ESP32 (QFN 5*5) are (30+j10) and (35+j10) Ω respectively. A π-type matching network is essential for antenna matching in the circuit design. CLC structure is recommended for the matching network.

  • Page 14: External Capacitor

    The schematics of Pin47 CAP2 and Pin48 CAP1 is shown in Figure 8. C5 (10 nF) that connects to CAP1 should be of high precision. For the RC circuit between CAP1 and CAP2 pins, please refer to Figure 8. Removing the RC circuit may slightly affect ESP32 in Deep-sleep mode. 3.3nF...

  • Page 15: Pcb Layout Design

    2. SCHEMATIC CHECKLIST AND PCB LAYOUT DESIGN 2.2 PCB Layout Design This chapter introduces the key points of designing ESP32 PCB layout with the example of ESP-WROOM-32D. The PCB layout design guidelines are applicable to cases when the • ESP32 module functions as a standalone device, and when the •...

  • Page 16: Positioning A Esp32 Module On A Base Board

    Base Board Figure 11: ESP32 Module Antenna Position on Base Board Note: As is shown in Figure 11, the recommended position of ESP32 module on the base board should be: • Position 3: Highly recommended; • Position 4: Recommended; • Position 1, 2, 5: Not recommended.

  • Page 17: Power Supply

    15 mm 15 mm Base Board Figure 12: Keepout Zone for ESP32 Module’s Antenna on the Base Board 2.2.1.3 Power Supply The 3.3V power traces are highlighted in yellow in Figure 13. The width of these power traces should be larger than 20 mil.

  • Page 18: Crystal Oscillator

    2. SCHEMATIC CHECKLIST AND PCB LAYOUT DESIGN Figure 13: ESP32 Power Supply Design 2.2.1.4 Crystal Oscillator For the design of the crystal oscillator section, please refer to Figure 14. In addition, the following should be noted: • The crystal oscillator should be placed far from the clock pin. The recommended gap is 2.7 mm. It is good practice to add high-density ground via stitching around the clock trace for containing the high-frequency clock signal.

  • Page 19: Esp32 Crystal Oscillator Layout

    2. SCHEMATIC CHECKLIST AND PCB LAYOUT DESIGN Figure 14: ESP32 Crystal Oscillator Layout 2.2.1.5 RF The characteristic RF impedance must be 50Ω. The ground plane on the adjacent layer needs to be complete. Make sure you keep the width of the RF trace consistent, and do not branch the trace. The RF trace should be as short as possible with dense ground via stitching around it for isolation.

  • Page 20: External Rc

    2.2.1.8 Touch Sensor ESP32 offers up to 10 capacitive IOs that detect changes in capacitance on touch sensors due to finger contact or proximity. The chip’s internal capacitance detection circuit features low noise and high sensitivity. It allows users to use touch pads with smaller area to implement the touch detection function.

  • Page 21: Esp32 As A Slave Device

    2.2.2 ESP32 as a Slave Device When ESP32 works as a slave device in a system, the user needs to pay more attention to signal integrity in the PCB design. It is important to keep ESP32 away from the interferences caused by the complexity of the system Espressif Systems ESP32 Hardware Design Guidelines V2.1...

  • Page 22: Typical Layout Problems And Solutions

    Wi-Fi radio. Therefore, the following should be noted with regards to the PCB design. • As can be seen in Figure 19, ESP32 should be placed near the edge of the PCB and away from the CPU and DDR, the main high-frequency noise sources. The distance between the chip and the noise sources decreases the interference and reduces the coupled noise.

  • Page 23: Q: The Power Ripple Is Small, But Rf Tx Performance Is Poor

    Rx performance. For instance, the crystal oscillator signal harmonics could couple to the antenna. If the Tx and Rx traces of UART cross over with RF trace, then, they will affect the Rx performance, as well. If ESP32 serves as a slave device, there will be other high-frequency interference sources on the board, which may affect the Rx performance.

  • Page 24: Hardware Development

    PCB area. The module integrates a 4-MB SPI flash. At the core of this module is the ESP32 chip*, which is a single 2.4 GHz Wi-Fi and Bluetooth combo chip designed with TSMC’s 40 nm ultra-low power technology. ESP32-PICO-D4 integrates all peripheral components seamlessly, including a crystal oscillator, flash, filter capacitors and RF matching links in one single package.

  • Page 25: Esp32-Wroom-32D(Esp-Wroom-32D) Module

    MP3 decoding. At the core of the module is the ESP32-D0WD chip. The size of the module is 18±0.2 mm x 25.5±0.2 mm x 3.1±0.15 mm. The flash used is in an SOP8-208 mil package.

  • Page 26: Esp32-Wrover Module

    3. HARDWARE DEVELOPMENT and MP3 decoding. At the core of the module is the ESP32-D0WD chip. ESP32-WROOM-32U is different from ESP32-WROOM-32D in that ESP32-WROOM-32U integrates a U.FL connector. The size of the module is 18±0.2 mm x 25.5±0.2 mm x 3.1±0.15 mm. The flash used is in an SOP8-208 mil package.

  • Page 27: Notes On Using Modules

    • The serial tool cannot be used for both the log-print and flash-download tools simultaneously. 3.7 ESP32-DevKitC Development Board ESP32-DevKitC is a small-sized ESP32-based development board. The board comes in two versions, either with ESP-WROOM-32 module or ESP32-WROVER/ESP32-WROVER-I module soldered.

  • Page 28: Esp-Wrover-Kit Development Board

    ESP-WROOM-32 and ESP32-WROVER. The ESP-WROVER-KIT features support for an LCD and MicroSD card. The I/O pins have been broken out from the ESP32 module for easy extension. The board carries an advanced multi-protocol USB bridge (the FTDI FT2232HL), enabling developers to use JTAG directly to debug ESP32 through the USB interface.
  • Page 29 3. HARDWARE DEVELOPMENT Figure 27: Rear Side of the ESP-WROVER-KIT Layout For more information on this board’s layout, schematics, etc., please refer to ESP-WROVER-KIT Getting Started Guide. Espressif Systems ESP32 Hardware Design Guidelines V2.1...

  • Page 30: Applications

    ESP32-DevKitC). 4.2 ESP32-PICO-KIT Mini Development Kit ESP32-PICO-KIT is a mini development board produced by Espressif. At the core of this board is the ESP32- PICO-D4, a System-in-Package (SIP) module with complete Wi-Fi and Bluetooth functionalities. All the IO signals and system power on ESP32-PICO-D4 are led out through two rows of 20 pads populated with CON20x2_2P54 pins.
  • Page 31 V1.2 Updated Section RF; Updated Figure ESP-WROOM-32 Pin Layout; Updated Table ESP-WROOM-32 Pin Definitions; Updated Section Notes. Updated the notice to Table ESP32 Pin Description; 2017.03 V1.3 Added a note to Table ESP-WROOM-32 Pin Definitions. Updated Section Strapping Pins; Updated Figure ESP32 Pin Layout (for QFN 5*5);...
  • Page 32 Date Version Release notes Deleted sections introducing protocols, applications, block diagram and pin de- scription of ESP32, for information of which please refer to ESP32 Datasheet; Updated all figures and description of schematics and PCB layout in Chapter Added Section 2.1.6...

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