jbaker0428/Unified-Robotics-Development-Board — Issue #8: MCU decoupling
Author: jbaker0428
Created: 2011-11-03 02:52:50+00:00
State: open

Need more decoupling capacitors for the microcontrollers. The XMOS specifies one per pin -- for layout reasons with the QFN package we can keep that to one per pair.

From the STM32 manual:
* The VDD pins must be connected to VDD with external decoupling capacitors; one single Tantalum or Ceramic capacitor minimum 4.7 µF typical 10 µF) for the package + one 100 nF Ceramic capacitor for each VDD pin).
* The VDDA pin must be connected to two external decoupling capacitors (100 nF Ceramic capacitor + 1 µF Tantalum or Ceramic capacitor).
* The VREF+ pin can be connected to the VDDA external power supply. If a separate, external reference voltage is applied on VREF+, a 100 nF and a 1 µF capacitor must be connected on this pin. To compensate peak consumption on Vref, the 1 µF capacitor may be increased up to 10µF when the sampling speed is low. When ADC or DAC is used, VREF+ must remain between 1.8 V and VDDA. VREF+ can be grounded when ADC and DAC are not active; this enables the user to power down an external voltage reference.