Power, Bypass caps

WIP

Bypass caps

This page expands further on the topic Power Demands of the ESP8266 by looking at Espressif's bypass capacitor recommendations.

The ESP8266 has two power supplies, analog and digital, broken out into 5 power supply rails: VDD3P3, VDDA, VDDD, VDD_RTC, and VDDPST. For VDD3P3 pins in addition to the usual 0.1μF bypass capacitor, their design guide recommends an additional 10 μF capacitor to support the RF Transmitter. See Section 1.4.1.2. and Section 1.6.3.1. Power Supply Design for note some worthy information.

• VDD3P3 - Amplifier Power 2.5 V to 3.6 V, used to power the RF transmitter and Receiver for WiFi.
• VDDA - Analog Power 2.5 V to 3.6 V
• VDDD - Analog Power 2.5 V to 3.6 V
• VDDPST - Digital/IO Power Supply 1.8 V to 3.3 V
• VDD_RTC - NC (1.1 V) - this pins floats, does not get connected

Read Espressif's Hardware Design Guideline, section 1.4.1 for more details.

In the Espressif's Hardware Design Guideline, section 1.4.1.2. the notes specify "When using a single power supply, the recommended output current is 500 mA." Not emphasized in their description is that the 500 mA is for peak demand (transient load) not continuous. Also, the various ESP Modules that I have seen are all using a single power supply. The transient nature of the load becomes a significant factor in understanding how such tiny LDO regulators, often less than the size of a small grain of rice, can supply 500mA. That is to say, the average load can comply with the LDO package power dissipation capability while the part can supply 500mA into short peak load demands, such as the WiFi transmit.