17.2.1 Power Supply Connections

The following figures shows the recommended power supply connections for switched/linear mode, linear mode only and with battery backup.

Table 17-1. Power Supply Connections, V_DDCORE From Internal Regulator
Signal Name	Recommended Pin Connection	Description
V_DDIO	1.8V to 3.6V Decoupling/filtering capacitors 100nF⁽¹⁾⁽²⁾ and 10µF⁽¹⁾ Decoupling/filtering inductor 10µH⁽¹⁾⁽³⁾	Digital supply voltage
V_DDANA	1.8V to 3.6V Decoupling/filtering capacitors 100nF⁽¹⁾⁽²⁾ and 10µF⁽¹⁾ Ferrite bead⁽⁴⁾ prevents the V_DD noise interfering with V_DDANA	Analog supply voltage
V_DDIN	1.8V to 3.6V Decoupling/filtering capacitors 100nF⁽¹⁾⁽²⁾ and 10µF⁽¹⁾ Decoupling/filtering inductor 10µH⁽¹⁾⁽³⁾	Digital supply voltage
V_BAT	1.8V to 3.6V when connected	External battery supply input
V_DDCORE	0.9V to 1.2V typical Decoupling/filtering capacitors 100nF⁽¹⁾⁽²⁾ and 1µF⁽¹⁾	Linear regulator mode: Core supply voltage output/ external decoupling pin
GND		Ground
GND_ANA		Ground for the analog power domain

These values are only given as a typical example.
Decoupling capacitors should be placed close to the device for each supply pin pair in the signal group, low ESR capacitors should be used for better decoupling.
An inductor should be added between the external power and the V_DD for power filtering.
A ferrite bead has better filtering performance compared to standard inductor at high frequencies. A ferrite bead can be added between the main power supply (V_DD) and V_DDANA to prevent digital noise from entering the analog power domain. The bead should provide enough impedance (e.g. 50Ω at 20MHz and 220Ω at 100MHz) to separate the digital and analog power domains. Make sure to select a ferrite bead designed for filtering applications with a low DC resistance to avoid a large voltage drop across the ferrite bead.