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ESP8684 Series
Hardware Design Guidelines
Introduction
Hardware design guidelines give advice on how to integrate ESP8684 into other products.
ESP8684 is a series of ultra-low-power Wi-Fi and Bluetooth
These guidelines will help to ensure optimal performance of your product with respect to tech-
nical accuracy and conformity to Espressif's standards.
®
5 (LE) SoCs.
www.espressif.com
Version 1.1
Espressif Systems
Copyright © 2022
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Summary of Contents for Espressif Systems ESP8684 Series
- Page 1 ESP8684 Series Hardware Design Guidelines Introduction Hardware design guidelines give advice on how to integrate ESP8684 into other products. ® ESP8684 is a series of ultra-low-power Wi-Fi and Bluetooth 5 (LE) SoCs. These guidelines will help to ensure optimal performance of your product with respect to tech- nical accuracy and conformity to Espressif’s standards.
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Page 2: Table Of Contents
3.7.4 Q: TX performance is not bad, but the RX sensitivity is low. Hardware Development ESP8684 Modules ESP8684 Development Boards Hardware Design Checklist Form Related Documentation and Resources Glossary Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... - Page 3 Contents Revision History Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback...
- Page 4 ESP8684 Analog Power Traces in a Four-layer PCB Design ESP8684 Crystal Oscillator Layout ESP8684 RF Layout in a Four-layer PCB Design ESP8684 PCB Stack up Design ESP8684 Stub in a Four-layer PCB Design Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback...
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Page 5: Overview
As a result, PCB size has been greatly reduced. With its advanced calibration circuitry, ESP8684 can dynamically adjust itself to remove external circuit imperfections or adapt to changes in external conditions. As such, the mass production of ESP8684 series does not require expensive and specialized Wi-Fi test equipment. -
Page 6: Schematic Checklist
Date: • Flash • Strapping pins • Clock source • RF • GPIO The rest of this document details the specifics of circuit design for each of these sections. Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... -
Page 7: Power Supply
VDDA3P3 pins so as to suppress high-frequency harmonics. The recommended rated current of the inductor is 500 mA or above. Refer to Figure and place the appropriate decoupling capacitor near each analog power pin. Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... -
Page 8: Power-On Sequence And System Reset
0.25 × VDD) V. VDD is the I/O voltage for a particular power domain of pins. To avoid reboots caused by external interferences, make the CHIP_EN trace as short as possible. Also, add a pull-up resistor as well as a capacitor to the ground whenever possible. Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... -
Page 9: Power-Up And Reset Timing
Duration of CHIP_EN signal level < V to reset the chip IL_nRST 2.3 Flash ESP8684 series is embedded with 1 MB, 2 MB, or 4 MB flash. It doesn’t need to connect to external flash for firmware. 2.4 Clock Source ESP8684 has two clock sources: •... -
Page 10: Rtc (Optional)
A π-type matching network is essential for antenna matching in the circuit design. CLC structure is recommended for the matching network. The parameters of the components in the matching network are Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... -
Page 11: Uart
Note: The content below is excerpted from Section Strapping Pins in ESP8684 Series Datasheet. ESP8684 series has two strapping pins: • GPIO8 • GPIO9 Software can read the values of GPIO8 and GPIO9 from GPIO_STRAPPING field in GPIO_STRAP_REG register. For register description, please refer to Section GPIO Matrix Register Summary in ESP8684 Technical Reference Manual. -
Page 12: Gpio
Table 3: Parameter Descriptions of Setup and Hold Times for the Strapping Pins Parameter Description (ms) Setup time before CHIP_EN goes from low to high Hold time after CHIP_EN goes high 2.9 GPIO Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... - Page 13 ESP8684 Technical Reference Manual. ESP8684 series has 14 GPIO pins which can be assigned various functions by configuring corresponding registers. Besides digital signals, some GPIOs can be also used for analog functions, such as ADC. All GPIOs have selectable internal pull-up or pull-down, or can be set to high impedance. When these GPIOs are configured as an input, the input value can be read by software through the register.
- Page 14 You may add pull-up and pull-down resistors in your PCB design referring to Table DC Characteristics (3.3 V, 25 °C) in ESP8684 Series Datasheet, or enable internal pull-up and pull-down resistors during software initialization. Notes • R - These pins have analog functions. Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback...
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Page 15: Pcb Layout Design
If module-on-board design is adopted, attention should be paid while positioning the module on the base board. The interference of the base board on the module’s antenna performance should be minimized. Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... - Page 16 Figure 11. If there is base board under the antenna area, it is recommended to cut it off to minimize its impact on the antenna. Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback...
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Page 17: Power Supply
• Four-layer PCB design is recommended over a two-layer design. The power traces should be routed on Layer 3 whenever possible. Vias are required for the power traces to go through the layers and get Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... -
Page 18: Crystal Oscillator
In addition, the following should be noted: • The crystal oscillator should be placed far from the clock pin to avoid the interference on the chip. The gap Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... - Page 19 Figure 14: ESP8684 Crystal Oscillator Layout 3.5 RF The RF trace is routed as shown highlighted in pink in Figure 15. Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback...
- Page 20 Note that a stub is not required for package types above 0201. • The ground plane on the adjacent layer needs to be complete. Do not route any traces under the RF trace whenever possible. Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback...
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Page 21: Uart
Add a 10 µF filter capacitor to the branch of the power trace (the branch powering the chip’s analog power pin). The 10 µF capacitor should be as close to the analog power pin as possible for small and stable current ripples. Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... -
Page 22: Q: The Power Ripple Is Small, But Rf Tx Performance Is Poor
Solution: Keep the antenna away from crystal oscillators. Do not route high-frequency signal traces close to the RF trace. Please see Section for details. Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... -
Page 23: Hardware Development
• The serial port cannot be used for both the log-print and flash-download tools simultaneously. 4.2 ESP8684 Development Boards For a list of the latest designs of ESP8684 boards please check Development Boards section of Espressif website. Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... -
Page 24: Hardware Design Checklist Form
To verify the compliance of your design with all the important hardware design guidelines, please refer to the checklist in Espressif Hardware Examination Form: https://www.espressif.com/en/contact-us/technical-inquiries/hardware-issues In case of doubt or discrepancy between this document and the checklist, this document shall prevail. Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... -
Page 25: Related Documentation And Resources
Find an Espressif hardware product suitable for your needs by comparing or applying filters. https://products.espressif.com/#/product-selector?language=en Contact Us • See the tabs Sales Questions, Technical Enquiries, Circuit Schematic & PCB Design Review, Get Samples (Online stores), Become Our Supplier, Comments & Suggestions. https://espressif.com/en/contact-us/sales-questions Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback... - Page 26 Real-Time Clock Receive System-in-Package Transmit Zero-ohm resistor A zero-ohm resistor is a placeholder on the circuit so that another higher ohm resistor can replace it, depending on design cases. Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback...
- Page 27 Revision History Revision History Date Version Release Notes 2022-05-20 v1.1 Added section RTC (optional) 2022-05-05 v1.0 First release 2022-01-10 v0.1 Draft Espressif Systems ESP8684 Series Hardware Design Guidelines v1.1 Submit Documentation Feedback...
- Page 28 The Wi-Fi Alliance Member logo is a trademark of the Wi-Fi Alliance. The Bluetooth logo is a registered trademark of Bluetooth SIG. All trade names, trademarks and registered trademarks mentioned in this document are property www.espressif.com of their respective owners, and are hereby acknowledged. Copyright © 2022 Espressif Systems (Shanghai) Co., Ltd. All rights reserved.
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