Place a minimum amount of decoupling
capacitance on VDD. See the CVDD TOTAL parameter in Power Management Module Electrical Data and Timing.
In external VREG mode, the actual amount of decoupling capacitance to use is a
requirement of the power supply driving VDD.
Either of the configurations outlined
below is acceptable:
- Configuration 1: Divide
CVDD TOTAL equally across the VDD pins. This option may be used
in internal VREG mode where it may be impossible to connect all the VDD pins
together on the PCB. Refer to Supply Pins Ganging section.
- Configuration 2: Install a
single decoupling capacitor with value of CVDD TOTAL. In this
configuration, all VDD pins must be connected to each other on the PCB.
Note: Having the decoupling capacitor
or capacitors close to the device pins is critical.