A novel and useful transmitter (TX) architecture for ultra-low power (ULP) radios. An all-digital PLL employs a digitally controlled oscillator (DCO) having switching current sources to reduce supply voltage and power consumption without sacrificing phase noise and startup margins. It also reduces 1/f noise allowing the ADPLL after settling to reduce its sampling rate or shut it off entirely during direct DCO data modulation. A switching power amplifier integrates its matching network while operating in class-E/F2 to maximally enhance its efficiency. The transmitter has been realized in 28 nm CMOS and satisfies all metal density and other manufacturing rules. It consumes 3.6 mW/5.5 mW while delivering 0 dBm/3 dBm RF power in Bluetooth Low-Energy.