Adc; External Capacitor - Espressif Systems ESP32 Hardware Design Manuallines

Chapter 3. Schematic Checklist
GPIO Pin Func-
Name tion
0
36 SEN- GPIO36
SOR_VP
37 SEN- GPIO37
SOR_CAPP
38 SEN- GPIO38
SOR_CAPN
39 SEN- GPIO39
SOR_VN
Reset:
• 0: IE=0 (input disabled)
• 1: IE=1 (input enabled)
• 2: IE=1, WPD=1 (input enabled, pull-down resistor)
• 3: IE=1, WPU=1 (input enabled, pull-up resistor)

3.9 ADC

Please add a 0.1 μF filter capacitor between ESP pins and ground when using the ADC function to improve accuracy.
When RTC peripherals (SAR ADC1/SAR ADC2/AMP) is powered on, the inputs of GPIO36 (SENSOR_VP) and
GPIO39 (SENSOR_VN) will be pulled down for approximately 80 ns. Therefore, it is recommended to use SEN-
SOR_VP and SENSOR_VN as ADC pins.
If SENSOR_VP and SENSOR_VN are used as GPIOs in the design, while ADC is supported by other pins, then
software should disregard the glitch. Optionally, make SENSOR_VP and SENSOR_VN active high pins.
ADC1 is recommended over ADC2 as the latter cannot be used when Wi-Fi function is enabled.
The calibrated ADC results after hardware calibration and
accuracy, you may implement your own calibration methods.
• When ATTEN=0 and the effective measurement range is 100 ~ 950 mV, the total error is ±23 mV.
• When ATTEN=1 and the effective measurement range is 100 ~ 1250 mV, the total error is ±30 mV.
• When ATTEN=2 and the effective measurement range is 150 ~ 1750 mV, the total error is ±40 mV.
• When ATTEN=3 and the effective measurement range is 150 ~ 2450 mV, the total error is ±60 mV.

3.10 External Capacitor

Figure ESP32 Schematic for External Capacitor
pin48 CAP1.
C5 (10 nF) that connects to CAP1 should be of 10% tolerance and is required for proper operation of ESP32.
RC circuit between CAP1 and CAP2 pins may be omitted under certain conditions. This circuit is used when entering
Deep-sleep mode. During this process, to minimize power consumption, the voltage to power ESP32 internals is
dropped from 1.1 V to around 0.7 V. The RC circuit is used to minimize the period of the voltage drop. If removed,
this process will take longer and the power consumption in Deep-sleep will be higher. If particular application of
ESP32 is not using Deep-sleep mode, or power consumption is less critical, then this circuit is not required.
Espressif Systems
Table 6 – continued from previous page
Func- Func- Func-
tion tion tion
1 2 3
– GPIO36 –
– GPIO37 –
– GPIO38 –
– GPIO39 –
software calibration
shows the schematic of components connected to pin47 CAP2 and
19
Submit Document Feedback
Func- Func- Reset
tion tion
4 5
– – 0
– – 0
– – 0
– – 0
are shown in the list below. For higher
Release master