The incorporation of flexPWR technology provides the ability to disable the internal +1.2V regulator.
When the regulator is disabled, an external +1.2V must be supplied to the VDDCR pin.
Disabling the internal +1.2V regulator makes it possible to reduce total system power, since an external switching regulator with greater efficiency (versus the internal linear regulator) can be used to provide +1.2V to the transceiver circuitry.