Typical Layout Problems And Solutions; Q: The Current Ripple Is Not Large, But The Tx Performance Of Rf Is Rather Poor; Q: The Power Ripple Is Small, But Rf Tx Performance Is Poor - Espressif Systems ESP32-S2 Hardware Design Manuallines

3. PCB Layout Design
Note:
For more details on the hardware design of ESP32-S2 touch sensor, please refer to

3.10 Typical Layout Problems and Solutions

3.10.1 Q: The current ripple is not large, but the TX performance of RF is rather poor.

Analysis:
The current ripple has a strong impact on the RF TX performance. It should be noted that the ripple must be
tested when ESP32-S2 is in the normal working mode. The ripple increases when the power gets high in a
different mode.
Generally, the peak-to-peak value of the ripple should be <80 mV when ESP32-S2 sends MCS7@11n packets,
and <120 mV when ESP32-S2 sends 11m@11b packets.
Solution:
Add a 10 µF filter capacitor to the branch of the power trace (the branch powering the ESP32-S2 analog power
pin). The 10 µF capacitor should be as close to the analog power pin as possible for small and stable current
ripples.

3.10.2 Q: The power ripple is small, but RF TX performance is poor.

Analysis:
The RF TX performance can be affected not only by power ripples, but also by the crystal oscillator itself. Poor
quality and big frequency offsets of the crystal oscillator decrease the RF TX performance. The crystal oscillator
clock may be corrupted by other interfering signals, such as high-speed output or input signals. In addition, high-
frequency signal traces, such as the UART trace under the crystal oscillator, could also result in the malfunction of
the crystal oscillator. Besides, sensitive components or radiation components, such as inductors and antennas,
may also decrease the RF performance.
Solution:
This problem is caused by improper layout and can be solved by re-layout. Please see Section
Espressif Systems
Touch sensor (TOUCH1 ~ TOUCH14)
Protective sensor (TOUCH1 ~ TOUCH14)
Shied electrode
Figure 21: Shied Electrode and Protective Sensor
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Touch Sensor Application
19 ESP32-S2 Hardware Design Guidelines V1.1
Note.
3 for details.