This paper describes an ultra-low-voltage Bluetooth low-energy (BLE) receiver (RX) front end with an on-chip micropower manager (μPM) to customize the internal voltage domains. It aims at direct powering by the sub-0.5-V energy-harvesting sources like the on-body thermoelectric, eliminating the loss and cost of the interim dc-dc converters. Specifically, the RX incorporates: 1) a two-stage power-gating low-noise amplifier with fully on-chip input-impedance matching and passive gain boosting reducing both the active and sleep power; 2) a class-D voltage-controlled oscillator (VCO) in parallel with a class-C starter to secure a fast startup; and 3) a μ PM using ring-VCO-locked charge pumps and bandgap references to withstand the supply-voltage variation (0.18-0.3 V). Fabricated in 28-nm CMOS, the RX operates down to a 0.18-V supply, while exhibiting 11.3-dB NF and -12.5-dBm out-of-band IIP3. The VCO shows < -113 dBc/Hz phase noise at 2.5-MHz offset. The active and sleep power are 382 μW and 1.33 nW, respectively.