Chapter 5. Hardware related
• GPIO6 ~ GPIO11 are saved for ash.
• GPIO1 and GPIO3 are the TX and RX pins for UART0, which cannot be congured.
• GPIO16 and GPIO17 are saved for PSRAM if there is any.
5.3.4 What is the voltage tolerance of GPIOs of ESP chips?
• The voltage tolerance of GPIO is 3.6 V. If the voltage exceeds 3.6 V, please add a voltage divider to protect
GPIO pins from damage.
5.3.5 What are the power supply specications for ESP8266?
• Digital working voltage range: 1.8 V ~ 3.3 V
• Analog working voltage range: 3.0 V ~ 3.6 V (the lowest possible value is 2.7 V)
• Peak analog circuit current: 350 mA
• Peak digital circuit current: 200 mA
Note: The operating voltage of SPI ash should be compatible with that of GPIO pins. The operating
voltage of CHIP_EN ranges from 3.0 V to 3.6 V, so please use a level converter when GPIO pins operates
at 1.8 V.
5.3.6 Do Espressif Wi-Fi modules support single-layer PCBs?
• The ESP32 module is a wireless device, which needs rather high-quality PCB materials to fulll the RF per-
formance requirements. We have tested four-layer and two-layer PCBs, but not single-layer ones.
• Single-layer PCBs are not recommended as RF performance cannot be guaranteed. You may use single-layer
PCBs in your end products and then mount Espressif modules.
• Four-layer PCBs are recommended for desired RF performance.
5.3.7 What should be noted when I power ESP8266 with batteries?
• The operating voltage of ESP8266 ranges from 3.0 V to 3.6 V, so two AA batteries can be used to power
ESP8266. Please ensure the battery voltage stays within the operating range of ESP8266 when it drops.
• If the lithium battery voltage surpasses module operating voltage, and the voltage drops heavily during dis-
charge, then such batteries should not be used to power ESP8266.
• We recommend you to use DC/DC converters or LDO regulators to convert voltage before powering ESP8266.
Please pay attention to the dierence between the input and output voltages of converters or regulators.
5.3.8 Where can I get the footprint of ESP32 Series?
You may get the footprint in the PCB layout of dierent modules. Please refer to reference designs.
Espressif Systems 156
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